Systems and Methods for Intra-Operative Image Analysis

ABSTRACT

A system and method for analyzing images to optimize orthopaedic functionality at a site within a patient, including obtaining at least a first, reference image of the site, or a corresponding contralateral site, the first image including at least a first anatomical region or a corresponding anatomical region. At least a second, intra-operative results image of the site is obtained. At least one stationary base with at least two base points is selected to serve as a reference for both images during analysis including at least one of scaling, calculations, and image comparisons.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application No.61/944,520 filed 25 Feb. 2014, U.S. Provisional Application No.61/948,534 filed 5 Mar. 2014, U.S. Provisional Application No.61/980,659 filed 17 Apr. 2014, U.S. Provisional Application No.62/016,483 filed 24 Jun. 2014, U.S. Provisional Application No.62/051,238 filed 16 Sep. 2014, U.S. Provisional Application No.62/080,953 filed 17 Nov. 2014, and U.S. Provisional Application No.62/105,183 filed 19 Jan. 2015 which are incorporated by reference hereinin their entireties.

FIELD OF THE INVENTION

The invention relates to analysis of images of features within a patientand more particularly to accurately scaling and/or analyzing such imagesduring surgery.

BACKGROUND OF THE INVENTION

Orthopaedic surgeons and other healthcare professionals commonly rely onsurgical guidance techniques that can be broadly classified in twocategories: pre-operative digital templating or training systems thatenable pre-surgical planning, and computer-assisted navigation systemsproviding intra-operative guidance for placement and movement ofsurgical instruments within a patient. There are benefits to both ofthese technologies, but each has respective limitations.

Preoperative digital templating techniques enable preoperative surgicalplanning by utilizing digital or hard copy radiographic images orsimilar X-ray-type, scaled according to an object of known size.Commonly, a spherical ball marker of known size is placed between thelegs or next to the hip of a patient undergoing hip surgery so that itappears in the image; the ball marker is then utilized as a referencefeature for image scaling. This preoperative scaling technique hasinherent limitations to accuracy because it assumes that the boneswithin a patient and the surface ball marker will magnify at the sameratio. Commonly, the surgeon will realize during the surgery that thisscale factor is inaccurate, due to deviations in magnification ratios,rendering the preoperative template ineffective for intraoperativedecision making. For emergency cases such as hip fractures, preoperativedigital templating often cannot be utilized, because the X-ray imagesare taken in a hospital setting without utilizing a ball marker or otherscaling device.

Surgeons also have the option of utilizing computer-assisted navigationsystems which provide intraoperative guidance. The purported benefits ofcomputer navigation include reduction of outliers and adverse outcomesrelated to intraoperative positioning of surgical hardware. For example,computer navigation is utilized in hip replacement surgery to addprecision to implant positioning by providing data on functionalparameters such as leg length and offset changes during surgery.

Despite obvious clinical benefit, these systems have had limitedadoption due to their expense, the learning curve and trainingrequirements for surgeons and, for some systems, the additionalprocedure and time associated with hardware insertion into the patient.These adoption barriers have limited the use of computer assistednavigation to an extremely small percentage of overall hip arthroplastysurgeries. The surgeons that do not use these systems are limited totraditional techniques that are generally based on visual analysis andsurgeon experience. However, these techniques are inconsistent, oftenleading to outliers in functional parameters which may affect patientsatisfaction and implant longevity.

Details of one such technique, specifically used in a minimally invasivehip arthroplasty technique referred to as the direct anterior approach,are mentioned in the description of a total hip arthroplasty surgery, byMatta et al. in “Single-incision Anterior Approach for Total hipArthroplasty on an Orthopaedic Table”, Clinical Ortho. And Related Res.441, pp. 115-124 (2005). The intra-operative technique described byMatta et al. is time-consuming and has a high risk of inaccuracy due todifferences in rotation, magnification and/or scaling of various images.The high risk of inaccurate interpretation using this technique haslimited its utility in guiding surgical decision making.

What appears to be a software implementation of this technique isdescribed by Penenberg et al. in U.S. Patent Publication No.2014/0378828, which is a continuation-in-part application of U.S. Pat.No. 8,831,324 by Penenberg. While the use of a computer system mayfacilitate some aspects of this technique, the underlying challenges tothe technique are consistent with the challenges to Malta's approach,and limit the system's potential utility.

There are various other examples of where intra-operative guidancesystems could improve quality of patient care in orthopaedics throughthe reduction of outliers. One such example is in the treatment ofperitrochanteric hip fractures. The selection of the proper implant andassociated neck-shaft angle is often incompletely evaluated by thesurgeon and implant representative utilizing conventional techniques.Furthermore, variations in placement of screws and other fixationdevices and implants can significantly alter patient outcomes intreatment of these fractures. These variations and resulting outcomesare analyzed by Baumgaertner et al. in “The Value of the Tip-ApexDistance in Predicting Failure of Fixation of Peritrochanteric Fracturesof the Hip”, J. Bone Joint Surg. 77-A No. 7, pp. 1058-1064 (1995). Othertechniques relating to femoral fractures, including measurement of tipapex distance and screw position, are discussed by Bruijin et al. in“Reliability of Predictors for Screw Cutout in Intertrochanteric HipFractures”, J. Bone Joint Surg. Am. 94, pp. 1266-72 (2012).

Proper reduction of fractures, that is, proper alignment of bones duringsurgery, often leads to more consistent patient outcomes, andintraoperative analysis of such reductions is incompletely evaluatedcurrently because of the lack of non-invasive technologies that enableintraoperative analysis. One example is in the treatment of distalradius fractures. As referenced by Mann et al, “Radiographic evaluationof the wrist: what does the hand surgeon want to know?” Radiology,184(1), pp 15-24 (1992), accurate restoration of certain parameters,such as radial inclination, radial length and Palmar Slope or Tilt,during the treatment of distal radius fractures is important. Currently,intraoperative images are utilized by surgeons, but there is no abilityto readily analyse these parameters and form comparative analysis tonormal anatomy.

Given the inherent scaling limitations of preoperative surgical planningand adoption barriers of current intraoperative computer navigationsystems, an opportunity exists for a system and method that providesaccurate intraoperative guidance and data, but without the barriers toadoption and invasive hardware requirements of traditionalcomputer-assisted navigation.

It is therefore desirable to have a system and method to effectivelyscale and adjust images intra-operatively using comparative anatomicalfeatures, to enhance patient quality of care by providing accurateintra-operative guidance and data.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a system and method toaccurately and effectively scale, adjust and/or perform calculations onimages of anatomical features and/or implants such as prosthetic devicesduring surgery.

Another object of the present invention is to provide image analysis andfeedback information to enable more accurate planning, better fracturereduction, and/or optimal implant selection during the surgery.

Yet another object of the present invention is to capture and preserve adigital record of patient results for data collection and qualityimprovements in surgical procedures.

A still further object of the present invention is to improve theoutcome of bone repositioning, fracture repair, and/or fixation within apatient.

This invention results from the realization that intraoperative scalingand other analysis of a primary image and at least one secondary imagecan be more accurately accomplished based on an object of knowndimension which, along with at least two points that are consistent inthose images, can facilitate precise scaling and other analysis of thesecondary image in addition to the primary image as needed. At least oneof the primary image and the secondary image is a results image takenduring a surgical procedure on a portion of a patient. Further, at leastanother of the primary and secondary images is a reference imageincluding (i) a preoperative ipsilateral image and/or (ii) acontralateral image, taken before or during surgery, of a comparableportion of the patient.

This invention features a system to analyze images at a surgical sitewithin a patient, including an image selection module to acquire (i) atleast a first, reference image including one of a preoperative image ofthe surgical site and a contralateral image on an opposite side of thepatient from the surgical site, and (ii) at least a second, resultsimage of the site. The system further includes a data input module thatreceives the first and second images and generates at least two pointsto establish a first stationary base and a second stationary base on atleast one anatomical feature that is present in each of the first andsecond images, respectively, and an analysis module that utilizes thestationary base in each image to provide at least one of (a) overlayingthe first and second images and comparing at least one of bonealignment, scaling and implant alignment within the images and (b)analyzing at least one of image rotation, image alignment, scaling,offset, abduction angle, length differential and orientation of at leastone of a bone and an implant within the images.

In some embodiments, the first and second images are provided by theimage selection module to the data input module in a digitized format.At least one dimension of each of the first and second stationary basesis retrievably stored in at least one storage medium as a count ofpixels for that dimension, and the analysis module utilizes the pixelcount for that dimension. In certain embodiments, the analysis moduleutilizes the stationary base in a selected one of the first and secondimages to provide at least relative scaling of the other of the firstand second images to the match the scaling of the selected one of thefirst and second images. In one embodiment, the analysis module utilizesat least one object of known dimension in at least one of the first andsecond images to provide absolute scaling, that is, objective scalingaccording to a measurement system, to at least that image. In anembodiment, the analysis module rotates at least one of the first andsecond images relative to the other of the first and second images sothat both images are aligned according to their respective stationarybases.

In a number of embodiments, the data input module generates at least onelandmark point for each image that is spaced from the stationary base inthat image, and the analysis module utilizes the landmark points toassist alignment of the first and second images relative to each other.In other embodiments, the analysis module utilizes the landmark pointsto position a digital template on at least one of the first and secondimages. In certain embodiments, the system further includes a templateinput module that provides at least one digital template that issuperimposed over at least one feature in at least one of the first andsecond images. In some embodiments, the at least one digital template ismatched to at least one feature in each of the first and second images.In one embodiment, at least one digital template is matched to animplant in the second, results image and then the digital template issuperimposed on the first, reference image to analyze at least oneparameter such as abduction angle, offset, and/or length differential ofat least one bone of the patient. Preferably, the system furtherincludes a display to provide at least visual guidance to a user of thesystem.

In one embodiment, the first image is a contralateral image that isflipped and overlaid on the second image and, in another embodiment, thefirst image is a contralateral image, the data input module generates acommon stitching line in each image, typically separate from thestationary base established in each image, and the first and secondimages are stitched together to form a unitary view of both sides of thepatient. In some embodiments, scaling or rescaling of at least one ofthe images is accomplished by measuring a portion of an anatomicalfeature during surgery, such as a femoral head, and comparing themeasured feature to an initial, preoperative image which includes thatfeature. In other embodiments, scaling or rescaling is accomplished byidentifying at least one known dimension of an implant with anintraoperative image including that implant and then scaling accordingto that known dimension.

This invention further features a system and method for analyzing imagesto optimize the restoration of orthopaedic functionality, whileminimizing failures and patient discomfort, by providing intraoperativecomparison including calculations, scaling and/or rescaling for at leastone operative, results image of a site within a patient taken duringsurgery. The operative or results image is compared with at least onereference image of (i) a preoperative ipsilateral image and/or (ii) acontralateral image, taken before or during surgery, of comparableportions of a patient. At least one stationary base is selected in eachimage to serve as a reference during the image comparisons and/orscaling.

In certain embodiments, the system and method include optimizing thesizing and placement of an implant at the site within the patient. Thestep of analyzing includes estimating an optimally-configured implant,and the method further includes selecting a final implant based on theoptimally-configured implant. Certain embodiments further includegenerating an estimated measurement of the first anatomical featureutilizing the first image, and scaling the first image includescalculating a difference between the estimated measurement and thedirect measurement. In some embodiments, an initial scaling is re-scaledbased on the direct measurement.

In a number of embodiments, the step of analyzing the placement includescomparing the second image with the accurately scaled first image on amobile computing device. In one embodiment, the step of analyzingincludes comparing the first anatomical feature with a correspondingcontra-lateral anatomical feature of the patient, such as a joint on theopposite side of the patient. In certain embodiments, the firstanatomical feature is located on a portion of a bony part of the patientto be replaced, such as a femoral head, and obtaining the directmeasurement includes excising the bony part from the patient, andmeasuring the first anatomical feature substantially along the firstviewing angle. In some embodiments, a guidance system is provided toadjust the viewing area of one image on a screen to track actions madeby a user to another image on the screen, such as to focus or zoom in onselected landmarks in each image. In certain embodiments, at least oneof abduction angle and anteversion is calculated. In certainembodiments, error analysis and/or correction is provided for at leastone image, such as providing a confidence score or other normalizednumeric error analysis, and/or a visual representation of at least oneerror value or error factor, such as relative alignment of one or moregeometric shapes or symbols in two or more images.

This invention also features a system and method for analyzing images tooptimize the restoration of orthopaedic functionality at a surgical sitewithin a patient, including at least one of capturing, acquiring,selecting and receiving to provide: (i) at least a first, referenceimage along at least a first viewing angle including one of apreoperative image of the surgical site and a contralateral image on anopposite side of the patient from the surgical site; and (ii) at least asecond, results image of the site along the first viewing angle after asurgical procedure has been performed at the site. The system and methodfurther include generating on each of the first and second images atleast two points to establish a stationary base on a stable portion ofthe surgical site and identifying at least one landmark on anotherportion of the surgical site spaced from the stationary base, andproviding at least one of (a) an overlay of the first and second imagesto enable comparison of at least one of bone and implant alignmentwithin the images, (b) matching of at least one digital template to atleast one feature in each of the first and second images, and (c) anumerical analysis of at least one difference between points ofinterest, such as at least one of offset, length differential andorientation of at least one of a bone and an implant within the images.

BRIEF DESCRIPTION OF THE DRAWINGS

In what follows, preferred embodiments of the invention are explained inmore detail with reference to the drawings, in which:

FIG. 1 is a schematic image of a frontal, X-ray-type view of a pelvicgirdle of a patient illustrating various anatomical features;

FIG. 1A is a schematic image viewable on a display screen by a user of asystem and method according to the present invention, depicting atemplate image of a prosthesis superimposed over the upper portion of afemur in an X-ray image of the hip region of a patient;

FIG. 1B is an enlargement of the digital template image of FIG. 1A;

FIG. 2 is a image rendering similar to FIG. 1A after the digitaltemplate has been removed, illustrating measurement of a portion of thefemoral head utilizing a reference line;

FIG. 3 is a image similar to FIG. 1A after the digital template has beenre-scaled according to the present invention;

FIG. 4A is a schematic diagram of a system according to the presentinvention that interfaces with a user;

FIG. 4B is a schematic diagram illustrating how multiple types of userinterfaces can be networked via a cloud-based system with data and/orsoftware located on a remote server;

FIG. 4C is a high-level schematic diagram of a system according to thepresent invention;

FIG. 4D is a schematic diagram of the Intraoperative Analysis Module inFIG. 4C;

FIG. 4E is a schematic diagram of several variations of the SurgicalAnalysis Module in FIG. 4D;

FIG. 4F is a schematic diagram of the Intraoperative Rescaling Module inFIG. 4C;

FIG. 4G is a schematic diagram of an alternative Intraoperative AnalysisSystem according to the present invention;

FIG. 4H is a schematic diagram of an AP (Anterior-Posterior) PelvisReconstruction System according to the present invention;

FIG. 5 is a Flowchart A for the operation of Intraoperative Rescaling inone construction of the system and method according to the presentinvention;

FIG. 6 is a Flowchart B for an Anterior Approach for hip surgeryutilizing Flowcharts G and J;

FIG. 7 is a Flowchart G showing technique flow for both contralateraland ipsilateral analysis;

FIG. 8 is a Flowchart W of several functions performed for hip analysis;

FIG. 9 is an image of the right side of a patient's hip prior to anoperation and showing a marker placed on the greater trochanter as alandmark or reference point;

FIG. 10 is an image similar to FIG. 9 showing a reference line, drawn on(i) the pre-operative, ipsilateral femur or (ii) the contra-lateralfemur, to represent the longitudinal axis of the femur;

FIG. 11 is an image similar to FIG. 10 with a line drawn across thepelvic bone intersecting selected anatomical features;

FIG. 12 is a schematic screen view of two images, the left-hand imagerepresenting a pre-operative view similar to FIG. 10 and the right-handimage representing an intra-operative view with a circle placed aroundthe acetabular component of an implant to enable rescaling of thatimage;

FIG. 13 is a schematic screen view similar to FIG. 12 indicating markingof the greater trochanter of the right-hand, intra-operative image as afemoral landmark;

FIG. 14 is a schematic screen view similar to FIG. 13 with a referenceline drawn on the intra-operative femur in the right-hand view;

FIG. 15 is an image similar to FIGS. 11 and 14 with a line drawn acrossthe obturator foramen in both pre- and intra-operative views;

FIG. 16 is an overlay image showing the right-hand, intra-operativeimage of FIG. 15 superimposed and aligned with the left-hand,pre-operative image;

FIG. 17 represents a screen viewable by the user during a surgicalprocedure guided according to the present invention;

FIG. 18 is Flowchart J of AP Pelvis Stitching and Analysis;

FIG. 19 represents a screen view with a left-hand image of thecontra-lateral, left side of a patient having a line drawn on the pubicsymphysis;

FIG. 20 is a view similar to FIG. 19 plus a right-hand, intra-operativeimage of the right side of the patient, also having a line drawn on thepubic symphysis;

FIG. 21 shows the images of FIG. 20 overlaid and “stitched together” toreconstruct a view of the entire hip region of the patient

FIG. 22 is view similar to FIG. 21 with one reference line drawn acrossthe acetabular component of the image and another reference linetouching the lower portions of the pelvis

FIG. 23 is Flowchart L showing Intraoperative Guidance forIntertrochanteric Reduction and Femoral Neck Fractures according toanother aspect of the present invention, referencing Flowcharts M and N;

FIG. 24 is Flowchart M for Intertrochanteric Reduction Guidance,referencing Flowchart P;

FIG. 25 is Flowchart P for processing a Contralateral or IpsilateralImage;

FIG. 26 is a representation of a screen view with a left-hand image ofthe left, contralateral, “normal” side of a patient's hip regioninverted to resemble the right, “fractured” side of the patient andshowing marking of the lesser trochanter to serve as a femoral referencepoint;

FIG. 27 is a view similar to FIG. 26 showing drawing of a line acrossthe obturator foramen for overlay reference;

FIG. 28 is a view similar to FIG. 27 showing measurement of neck shaftangle;

FIG. 29 is a screen view with the left-hand image similar to FIG. 28 anda right-hand image of the fractured side of the patient, showing markingof the lesser trochanter on the fractured side;

FIG. 30 is a view similar to FIG. 29 showing marking of the obturatorforamen of the fractured side;

FIG. 31 is a view similar to FIG. 30 showing measurement of neck shaftangle on the fractured side;

FIG. 32 is a combined image showing the fractured side image overlaid onthe normal, inverted side image;

FIG. 33 is Flowchart N showing scaling and measurement as referenced inFlowchart L;

FIG. 34 represents a screen view of an image of a screw implanted totreat an inter-trochanteric hip fracture, showing measurement of thescrew;

FIG. 35 is a view similar to FIG. 34 showing measurement of Tip-Apexdistance in an AP image;

FIG. 36 is a view similar to FIG. 35 plus a lateral view on theright-hand side of the screen, showing measurement of the screw;

FIG. 37 is a view similar to FIG. 36 showing measurement of Tip-Apexdistance in the right-hand image;

FIG. 38 is a combined “Intertroch” view showing both Tip-Apex Analysisand Neck Shaft Analysis;

FIG. 39 is Flowchart Q of Intraoperative Guidance for Distal RadiusFracture Reduction according to another aspect of the present invention,referencing Flowcharts R and S;

FIG. 40 is Flowchart R showing Radial Inclination and Length ReductionGuidance, and referencing Flowchart T;

FIG. 41 is Flowchart S showing Palmar Slope Reduction Guidance;

FIG. 42 is Flowchart T showing identification of various anatomicalfeatures in the wrist and image processing;

FIG. 43 represents a screen view of an image of a “normal” wrist of apatient with a line drawn on the radius to indicate its central axis;

FIG. 44 is a view similar to FIG. 43 with marking of selected anatomicalpoints;

FIG. 45 is a view similar to FIG. 44 with a reference line drawn acrossthe carpal bones to provide a stationary base reference;

FIG. 46 is a view of an image of the normal wrist rotated to draw PalmarTilt;

FIG. 47 is a screen view with the left-hand image similar to FIG. 45 anda right-hand image of the fractured side of the patient, showing markingof the central axis of the radius on the fractured side;

FIG. 48 is a view similar to FIG. 47 showing marking of anatomicalpoints on the fractured side;

FIG. 49 is a view similar to FIG. 48 with a reference line drawn acrossthe carpal bones on the fractured side;

FIG. 50 is a screen view with the left-hand image similar to FIG. 46 anda right-hand image of the fractured wrist rotated to draw Palmar Tilt;

FIG. 51 is a combined view as a Distal Radius Report according to thepresent invention;

FIG. 52 is an image similar to FIG. 15 with points marking the lowestpoint on the ischial tuberosity and points marking the obturator foramenand top of the pubic symphysis in both pre- and intra-operative views;

FIG. 53 is an overlay image showing the right-hand, intra-operativeimage of FIG. 52 superimposed and aligned with the left-hand,pre-operative image utilizing triangular stable bases;

FIG. 54 is a schematic combined block diagram and flow chart of anidentification guidance module utilized according to the presentinvention;

FIG. 55 is a schematic block diagram of modules that analyze theorientation of a component such as an acetabular cup to generateabduction angle and anteversion information;

FIG. 56 is an image of an acetabular cup positioned in the leftacetabulum of a patient with a circle drawn around its hemisphericalsurface to provide diameter information;

FIG. 57 is an image similar to that of FIG. 56 with a line segment drawnunder the cup to calculate abduction angle relative to a neutral axisline;

FIG. 58 is an image similar to that of FIG. 57 with arcs drawn at thebottom of the acetabular cup to assist calculation of anteversion;

FIG. 59 is a Flowchart X of abduction angle and anteversion analysis bythe modules of FIG. 55 relative to the images of FIGS. 56-58

FIG. 60 is a schematic screen view of an image of the right side of apatient's hip prior to an operation and showing a mark placed on thegreater trochanter as a landmark or reference point according to thepresent invention;

FIG. 61 represents a screen viewable by the user during a surgicalprocedure guided according to the present invention showing two images,the left-hand image representing a pre-operative view similar to FIG. 60and the right-hand image representing an intra-operative view with acircle placed around the acetabular component of an implant to enablescaling or rescaling of that image based on an object of known size;

FIG. 62 is a schematic screen view similar to FIG. 61 indicating markingof the lateral shoulder of the prosthesis of the right-hand,intra-operative image, also with the greater trochanter marked in bothimages as a femoral landmark;

FIG. 63 is a schematic screen view similar to FIG. 62 with a referencebox indicating an acetabular template generated on top of the acetabularcomponent of the prosthesis on the intra-operative femur in theright-hand view;

FIG. 64 is a schematic screen view similar to FIG. 63 with theacetabular template now rendered in a precise location across thefemoral head in the preoperative view, using intraoperative datagathered during the step represented by FIG. 63;

FIG. 65 is a schematic screen view similar to FIG. 64 showing theacetabular component outline overlaid on the femoral head on theleft-hand, preoperative image with an overlay image of the prosthesissuperimposed and aligned with the femoral stem of the prosthesis in theright-hand, intra-operative image;

FIG. 66 is a schematic screen view similar to FIG. 65 showing thefemoral stem template placed on the pre-operative image, utilizingintraoperative data gathered in the step represented by FIG. 65, withintraoperative Offset and Leg Length calculations;

FIG. 67 is a schematic diagram of an Intra-operative Analysis Moduleaccording to the present invention to implement the Templating Techniquegenerating images as shown above in FIGS. 60-66;

FIGS. 68A and 68B are a Flowchart U showing Intraoperative TemplatingFlow within the Module of FIG. 67;

FIG. 69 is a Flowchart Y showing functions applied to the pre-operativeand intraoperative hip images for Intraoperative Templating of FlowchartU; and

FIG. 70 is an image of a trial implant in a hip with the acetabularcomponent transacted by a stationary base line and with two erroranalysis triangles.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

This invention may be accomplished by a system and method that providesintraoperative guidance via analysis including at least one of scaling,calculations, comparisons, and alignment for operative images takenduring surgery by comparing them with preoperative ipsilateral imagesand/or contralateral images, taken before or during surgery, ofcomparable portions of a patient. At least one stationary base isselected in each image to serve as a reference during the imageanalysis. Broadly, some techniques according to the present invention,referred to by the present inventors as “Image Overlay”, place one imageover another image during analysis to generate a combined overlappedimage, while certain other techniques according to the presentinvention, referred to by the present inventors as “Reverse Templating”or “Templating Technique”, place a digital template first on aproperly-scaled intra-operative image and then on a scaled pre-operativeimage during analysis.

In general, accurate analysis of two images of a patient is directlyrelated not only to how similar the two images are, but also howsimilarly the images are aligned with respect to scale, rotation, andtranslation. Using conventional techniques, a user would have tomanually adjust the images and/or retake multiple images to achieve thisgoal, something that would be difficult to do reliably and accurately.Utilizing two or more points as a stationary base according to thepresent invention in each image enables accurate analysis of the twoimages. Furthermore, the present Image Overlay technique can analyze how“similar” these images are to give the user feedback as to how accuratethe results are, that is, to provide a confidence interval.

To obtain useful information, the images (the “intraop” intra-operativeimage and a “preop” pre-operative image, for example) must be scaledsimilarly and preferably rotated similarly. If the scale is off, thiswill lead to error unless re-scaled properly. If the rotation is off,the user is likely to spend significant time “eyeballing” to manuallyalign the digital template on the preop image to match the intraopposition during Reverse Templating according to the present invention.Use of one or more landmarks, such as the teardrop of the pelvis and/orthe greater trochanter of the femur for hip-related surgery, accordingto the present invention aids in automated and accurate superimposing ofa template onto the preop image to match the intraop position of animplant and superimposed digital template during Reverse Templating. Forexample, the teardrop helps accurately place the acetabular template andthe greater trochanter helps place the femoral template at the rightlevel on each image. As compared to the present Image Overlay technique,the present Reverse Templating technique is less sensitive to howsimilar the images are, and therefore has a wider breadth of use asimages can be taken in different settings, such as comparing a preopimage taken in a physician's office with an intraop image taken duringhip surgery involving a posterior approach or other surgical procedure.

In some implementations, a system and method according to the presentinvention analyzes images to provide guidance to optimize therestoration of orthopaedic functionality at a surgical site within apatient, including capturing, selecting or receiving: (i) at least afirst, reference image along at least a first viewing angle includingone of a preoperative image of the surgical site and a contralateralimage on an opposite side of the patient from the surgical site; and(ii) at least a second, results image of the site, preferably also alongthe first viewing angle, after a surgical procedure has been performedat the site. The system and method further include generating on each ofthe first and second images at least two points to establish astationary base on a stable portion of the surgical site and identifyingat least one landmark on another portion of the surgical site spacedfrom the stationary base, and providing at least one of (a) an overlayof the first and second images to enable comparison of at least one ofbone and implant alignment within the images, (b) matching of at leastone digital template to at least one feature in each of the first andsecond images, and (b) a numerical analysis of at least one differencebetween points of interest, such as an analysis of at least one ofoffset, length differential and orientation of at least one of a boneand an implant within the images.

Establishing at least three points for the stationary base, such asdescribed below in relation to FIG. 70, is especially useful fordetermining rotational differences between images. One or more pointsmay be shared with points establishing a scaling line. Preferably, atleast one landmark is selected that is spaced from the stationary basepoints to increase accuracy of overlaying and/or comparing images.

In some constructions, scaling, which includes rescaling in someimplementations, of at least one of the images is accomplished bymeasuring an anatomical feature during surgery, and comparing themeasured feature to an initial, preoperative image which includes thatfeature. In other constructions, scaling or rescaling is accomplished bycomparing an intraoperative image with at least one known dimension of(i) an implant feature, such as the diameter of an acetabular cup or ascrew, or (ii) a temporarily-positioned object such as a ball marker ora tool such as a reamer. Typically, scaling or rescaling is accomplishedby establishing two points on a feature, generating a line between thetwo points, and determining the correct length for the line.

In certain constructions utilizing implants, especially prostheses, thecombination of accurately scaled templating, together with an innovativeapproach of combining a software-driven system according to the presentinvention with intra-operative medical imaging such as digital X-rayimages, dramatically improves the accuracy of various surgeries,especially difficult-to-see anterior approach surgery for total hipreplacement. The present invention enables a surgeon to compensate forunintended variations such as how a reamer or other tool interacts witha bone during preparation of the surgical site before or duringinsertion of the implant. In some constructions, the surgeon or otheruser is able to compare a pre-operative or intra-operative X-ray-typeimage of a patient's anatomy with an initial intra-operative X-ray-typeimage of a trial prosthesis, and deduce changes of offset and/or leglength to help guide surgical decision making. This unique process willgreatly improve patient satisfaction by increasing the accuracy ofdirect anterior surgery and other types of surgeries, and greatlyincrease surgeon comfort in performing these less-invasive procedures.

In some implementations, a system and method according to the presentinvention includes an inventive alternative “Reverse Templating”methodology for analyzing parameters such as abduction angle,intraoperative leg length and offset changes using a differentapplication of the stationary base, intraoperative scaling andanatomical landmark identification techniques. For Reverse Templatingimplementations, the system and method combines the use ofintraoperative data, gathered from intraoperative image analysis, withintraoperative templating on a preoperative ipsilateral image. Themethod can be applied in a wider range of hip arthroplasty surgeriesbecause it is less sensitive to inconsistencies in preoperative andintraoperative image acquisition, allowing the user to apply this systemand method during arthroplasty in the lateral position (i.e. posteriorapproach). This alternative system and method also enables a user toprecisely analyze, intraoperatively, how a potential change in implantselection would affect parameters such as abduction angle, offset and/orleg length. In this approach, described below in relation to FIGS.60-69, the user will analyze the preoperative ipsilateral andintraoperative images ‘side by side’, without the need to overlap theimages themselves. The system will scale and align these images relativeto one another using at least intraoperative data, and then analyzeoffset and leg length changes by combining intraoperative data with aunique utilization of digital prosthetic templates.

For image analysis according to the present invention, preferably atleast one stationary base and at least one anatomical landmark areselected. The term “stationary base”, also referred to herein as a“stable base”, means a collection of two or more points, which may bedepicted as a line or other geometric shape, drawn on each of two ormore images that includes at least one anatomical feature that ispresent in the two or more images of a region of a patient. For example,different images of a pelvic girdle PG of a patient, FIG. 1, typicallyshow one or both obturator foramen OF and a central pubic symphysis PS,which the present inventors have recognized as suitable reference pointsor features for use as part of a stationary base according to thepresent invention. Other useful anatomical features, especially to serveas landmarks utilized according to the present invention, includefemoral neck FN and lesser trochanter LT, shown on right femur F_(R),and femoral head FH and greater trochanter GT shown on left femur F_(L),for example. Femoral head FH engages the left acetabulum of the pelvicgirdle PG. Also shown in FIG. 1 are ischial tuberosities IT at thebottom of the ischium, a “tear drop” TD relating to a bony ridge alongthe floor of the acetabular fossa, and the anterior superior iliac spineASIS and the anterior inferior iliac spine AIIS of the ileum. Asdescribed below, carpal bones serve as a stationary base in images forradial bone fixation and other wrist-related procedures. In general,having a “non-movable” anatomical feature associated with the trunk of apatient is preferred for a stationary base, rather than a jointed limbthat can be positioned differently among two or more images.

In general, a longer stationary base is preferred over a shorterstationary base, because the longer base, especially if it is a line,will contain more pixels in images thereof and will increase accuracy ofoverlays and scaling according to the present invention. However, thefurther the stationary base is from the area of anatomical interest, thegreater the risk of parallax-induced error. For example, if the area ofinterest is the hip joint, then the ideal stationary base will be nearthe hip. In some procedures involving hip surgery, for example, astationary base line begins at the pubic symphysis PS, touches orintersects at least a portion of an obturator foramen OF, and extends to(i) the “tear drop” TD, or (ii) the anterior interior iliac spine AIIS.Of course, only two points are needed to define a line, so only tworeliable anatomical features, or two locations on a single anatomicalfeature, are needed to establish a stationary base utilized according tothe present invention. More complex, non-linear stationary bases mayutilize additional identifiable points to establish such non-linearbases.

Additionally, at least one identifiable anatomic “landmark”, or a set oflandmarks, is selected to be separate from the stationary base; the oneor more landmarks are utilized in certain constructions to analyze theaccuracy of the overlay process. This additional “landmark” preferablyis part of the stationary anatomy being anatomically compared. Forexample, the inferior portion of the ischial tuberosity IT can beidentified as an additional landmark. This landmark, in conjunction withthe stationary base, will depict any differences or errors in pelvicanatomy or the overlay which will enable the physician to validate, orto have more confidence in, the output of the present system.

The term “trial hip prosthetic” is utilized herein to designate aninitial implant selected by a surgeon as a first medical device toinsert at the surgical site, which is either the right side or the leftside of a patient's hip in this construction. In some techniques, thetrial prosthetic is selected based on initial digital templating similarto the procedure described below for FIGS. 1A-3, for example.

One technique for accomplishing the present invention is described inrelation to FIGS. 1A-3, which illustrate successive views or“screenshots” visible to a user of a system and method according to thepresent invention utilized for hip surgery. FIG. 1A is a schematicrepresentation of a screen view 10 depicting a digital template image 20of a prosthesis superimposed over the upper portion of a right femurF_(R). In some techniques a digitized X-ray image of the hip region of apatient along a frontal or anterior-to-posterior viewing angle isutilized for screen view 10 and, in other techniques, a digitalphotograph “secondary” image of a “primary” X-ray image of the hipregion of a patient along a frontal or anterior-to-posterior viewingangle is utilized for screen view 10. In one construction, screen view10 is shown on a computer monitor and, in another construction, is shownon the screen or viewing region of a tablet or other mobile computingdevice, as described in more detail below. Dashed line SK representsskin of the patient and provides an outline of soft tissues for thisviewing angle. Pelvic Girdle PG may also be referred to as a pelvis orhip.

Ball marker BM represents a spherical metal reference object of knowndimension placed between right leg RL and left leg LL, as traditionallyutilized to scale many types of medical images including X-ray images.Use of a ball marker or other non-anatomical feature is optional intechniques according to the present invention, as described in moredetail below. In particular, the present invention is useful forunplanned trauma surgery, where direct measurement of an anatomicalfeature, such as caliper measurements of an extracted femoral headduring emergency hip surgery, can be utilized by the present inventionto intraoperatively guide such surgery.

Template image 20 is shown in greater detail in FIG. 1B with a bodycomponent 22 including a stem 24, a fastener recess 26, and a support 28with a trunion 29, and an acetabular component 30 carried by support 28.Dashed line 32 indicates the longitudinal axis of support 28 and dashedline 34 indicates a longitudinal body axis for template image 20 to bealigned relative to a longitudinal axis of the femur F, as described inmore detail below.

Additional icons and reference elements are provided in thisconstruction, such as a reference line delete icon 40 for line 41, FIG.1A, a template body delete icon 42 and an acetabular component deleteicon 44 for body component 22 and acetabular component 30, FIG. 1B,respectively. One or more of these “virtual” items can be removed oradded to view 10 by a user as desired by highlighting, touching orclicking the “soft keys” or “soft buttons” represented by the icons. Incertain embodiments, one or more of the icons 40, 42 and/or 44 serves asa toggle to provide “on-off” activation or de-activation of thatfeature. Characters or other indicia 46, FIG. 1A, can be utilized todesignate image number and other identifying information. Other usefulinformation 48 can be shown such as Abduction Angle, Offset Changes andLeg Length Changes, as discussed in more detail below.

Screen view 51, FIG. 2, is similar to view 10 of FIG. 1A after thedigital template 20 has been removed, illustrating measurement of aportion of the femoral head FH of femur F_(R) utilizing a reference line60. Four indicator squares 52, 54, 56 and 58, also referred to asreference squares, navigation handles, or navigation points, areprovided in this construction to guide a user to draw the reference line60 in the viewing plane of screen view 51. In some constructions, a usertouches one of the squares 52-58 with a finger or a mouse cursor, andutilizes the square, such as by ‘dragging’ it, to move a marker to adesired location. This enables manipulation without blocking thelocation of interest.

Characters 70 such as “New Femoral Head Width” invite a user to enter adirect measurement into field 72, such as “50” to represent an actual 50mm caliper measurement for the dimension represented by line 60, asdescribed in more detail below. In this example, an initial scaling ofimage 51 had generated an estimated measurement of “45.6 mm” for line60. Other functional “soft buttons” are “Rescale” 74, “Retemplate” 76,“Cancel” 78 and “Done” 80. In other constructions, as described in moredetail below, intraoperative rescaling is conducted separately from ahip replacement process, and the direct measurement value, if needed, isutilized for intraoperative rescaling, for adjusting the template size,for comparing drawn lines, and other uses.

Direct measurement of the femoral head, such as with calipers, typicallyis conducted before a trial implant is inserted. The femoral headmeasurement enables (i) rescaling of the preoperative template or (ii)accurate scaling for the first time, especially where a preoperativetemplate has not been utilized. During overlay analysis, however,scaling is accomplished in some constructions by measuring or looking upa dimension of an implant, such as the radius or width of the acetabularcomponent of a hip prosthesis, for example.

FIG. 3 is an image of a view 90 similar to view 10 of FIG. 1A, along thesame viewing angle, after the digital template 20 has been re-scaledaccording to the present invention to a revised template 20′. In thisexample, reference line 41 was 13.1 mm in FIG. 1A, and reference line41′, FIG. 3, is now 14.3 mm as calculated by the system after re-scalingbased on the direct measurement. Also, for revised information 48′, theOffset Changes are re-calculated to be “0.9 mm” and the Leg LengthChanges are recalculated to be “4.1 mm”.

In one construction, the JointPoint Intraop™ system utilizes aninterpolation mapping approach with one or more reference points or“landmarks” to achieve template auto-rescaling. Certain importantlandmarks on a X-ray image, or on a photograph of an X-ray image, areused to anchor each fragment of a template. This is the basic model:

Σ₀ ^(m) P _(i)=Σ₀ ^(m) f(p _(i))  EQ. 1:

In this model, m is the number of landmarks, P_(i) is landmark afterinterpolation mapping, and p_(i) is the original landmark. f(p_(i)) isthe mapping function for rescaling.

$\begin{matrix}{{f\left( p_{i} \right)} = \frac{p_{i} - p_{1\; i}}{p_{2\; i} - p_{1\; i}}} & {{EQ}.\mspace{14mu} 2}\end{matrix}$

where P_(i1) and P_(i2) are two reference landmarks automaticallyprovided by program based on the size of x-ray image.

p _(1i) =└p _(i)×ratio┘EQ.3:

p _(2i) =┌p _(i)×ratio┐  EQ.4:

Where “ratio” is the comparison of size of a regulator in a target x-rayimage and a compared x-ray image. The regulator can be a ball marker, ora user-defined line or circle such as a circle drawn around anacetabular component.

$\begin{matrix}{{ratio} = \frac{{size}\mspace{14mu} {of}\mspace{14mu} {target}\mspace{14mu} {regulator}}{{size}\mspace{14mu} {of}\mspace{14mu} {compared}\mspace{14mu} {regulator}}} & {{EQ}.\mspace{14mu} 5}\end{matrix}$

By following the model indicated above, each of the template fragmentslands in the same position when the size of a template is changed and,therefore, users avoid the need to replace templates every time arescaling happens. Correct template placement can also be facilitated bystoring coordinates of a particular location on the femoral component ofa template, such as the midpoint of the top of the trunion 29 shown inFIG. 1B, for example.

In one implementation, a system 101 according to the present invention,FIG. 4A, has a user interface 103, a processor 105, and a communicationsmodule 107 that communicates with a remote server and/or other devicesvia a cloud 109, which represents a cloud-based computing system. Userinterface 103 includes a display 111, a user input module 113 and deviceinput 115 such as (i) a camera, to take a digital photo of afluoroscopic imaging screen, also referred to as a “fluoro” image, or ofa printed or otherwise fixed X-ray-type image, or (ii) a connection to aconventional medical imaging system (not shown). Display 111 is aseparate computer monitor or screen in some constructions and, in otherconstructions, is an integrated touch-screen device which facilitatesinput of data or commands of a user to processor 105. In someconstructions, user input 113 includes a keyboard and a mouse.

Processor 105 includes capability to handle input, module 119, to sendand receive data, module 121, and to render analysis and generateresults, module 123. Two-way arrows 117 and 125 represent wired orintegrated communications in some constructions and, in otherconstructions, are wireless connections. Communications module 107 has asend/upload module 127 and a receive/download module 129 to facilitatecommunications between processor 105 and cloud 109 via wired or wirelessconnections 125 and 131, respectively.

In some constructions, the present invention provides the ability toaccurately adjust implants and corresponding templates intra-operativelyby combining mobile-based templating functionality, utilizing a mobilecomputing device such as a tablet, a Google Glass™ device, a laptop or asmart phone wirelessly interconnected with a main computing device, anda unique scaling technique translating real life intra-operativefindings into selection of an optimally-configured implant for apatient. Preferably, the system includes a mode that does not requireconnection with a remote server, in the event of loss of interneconnectivity or other extended system failure.

FIG. 4B is a schematic diagram of system 141 according to the presentinvention illustrating how multiple types of user interfaces in mobilecomputing devices 143, 145, 147 and 149, as well as laptop 151 andpersonal computer 153, can be networked via a cloud 109 with a remoteserver 155 connected through web services. Another useful mobile imagingand computing device is the Google Glass wearable device. Data and/orsoftware typically are located on the server 155 and/or storage media157.

Software to accomplish the techniques described herein is located on asingle computing device in some constructions and, in otherconstructions such as system 141, FIG. 4B, is distributed among a server155 and one or more user interface devices which are preferably portableor mobile.

A system 200 according to the present invention, FIG. 4C, includes aUser Input Module 202 with one or more data items that are provided to aScaling Module 204, a Templating Module 206, an Intraoperative AnalysisModule 208, and a Display 210. Although Scaling Module 204 isillustrated and described as separate from Intraoperative Module 208 insome constructions, both Modules 204 and 208 can be considered as formsof analysis conducted according to the present invention utilizing astationary base generated on at least two images. Further, User Inputcan be considered as a data input module that generates at least twopoints to establish a stationary base on at least one anatomical featurethat is present in the images. In this construction, system 200 alsoincludes a storage media 212 which receives and/or provides data toModules 204, 206, 208 and Display 210. Scaling Module 204 includesStandard Preoperative Scaling unit 214, Intraoperative Scaling unit 216and Intraoperative Rescaling unit 218 in this construction and providesdata to Templating Module 206 and/or Display 210.

The Intraoperative Analysis Module 208 is illustrated in more detail inFIG. 4D with an Image Selection Module 220, a Stable Base IdentificationModule 222 which guides the selection of at least one stationary base,and a Landmark Identification Module 224. Module 222 providesinstructions to Overlay Module 226; Module 224 provides instructions tothe Overlay Module 226 and/or to an optional Longitudinal AxisIdentification Module 228, shown in phantom. When utilized, module 228communicates with Differential Analysis Module 230 which in turncommunicates with Surgical Analysis Module 232, shown in more detail inFIG. 4E. Overlay Module 226 communicates with Surgical Analysis Module232 either directly or via Differential Analysis Module 230.

Also optional and present in some constructions in the IntraoperativeAnalysis Module 208 is a Stable Base Error Analysis Module 2100 that canprovide outputs to Overlay Module 226 and/or Differential AnalysisModule 230. When utilized, the Stable Base Error Analysis Module 2100compares at least two images selected in Image Selection Module 220, andanalyzes error or differences between the anatomic structures thatcontain the stationary base points. The module 2100 provides visualand/or quantitative data of image inconsistencies, such as shown in FIG.70 below, providing guidance of how much value to place in the output ofIntraoperative Analysis Module 208, FIGS. 4C and 4D. Within the module2100, the system automatically, or the user manually, identifies one ormore anatomic error reference points located within the anatomicstructure selected to contain the stationary base. At least one of theerror reference points, but preferably all of them, must be separatefrom the points utilized to establish the stationary base. The twoimages are scaled, rotated and transformed utilizing the stationary baseaccording to the present invention. Because the error reference pointsidentified in this module 2100 are separate from the stationary basepoints used to align the images, but are on the same non-movableanatomic structure, differences in error reference point locationbetween the two images allow for the analysis within this module 2100.If the points seem extremely close, the anatomic structures are likelyto be positioned very consistently between the two images beinganalyzed. If points are further apart, such as shown and described inrelation to FIG. 70 below, then there are likely to be imaging and/oranatomic inconsistencies that may impact the data provided by theAnalysis Module 208.

FIG. 4E is a schematic diagram of several variations of the SurgicalAnalysis Module 232, FIG. 4D, depending on the surgical procedures to beguided according to the present invention. One or more of the followingmodules are present in different constructions according to the presentinvention: Hip Arthroplasty Module 240, Intertrochanteric ReductionAnalysis Module 242, Femoral Neck Reduction Analysis Module 244 and/orDistal Radius Fracture Reduction Analysis Module 246. In the illustratedconstruction, the Hip Arthroplasty Module 240 includes at least one ofan Ipsilateral Analysis unit 250 a, a Contralateral Analysis unit 252,an AP Pelvis Stitching and Analysis unit 254 and an alternativeContralateral Analysis unit 256 which communicates with an Image Flipunit 258 and an AP Pelvis Stitching and Analysis unit 260. In someconstructions, Ipsilateral Analysis module 250 a optionally providesinputs to a Reverse Templating Module 250 b, shown in phantom. HipArthroplasty is described in more detail below in relation to FIGS.6-17, with AP Pelvis Stitching and Analysis described in relation toFIGS. 18-22 below.

Intertrochanteric Reduction Analysis Module 242 includes a ContralateralAnalysis Module 270, a Neck Shaft Analysis unit 272 and a Tip ApexAnalysis unit 274 in this construction. Femoral Neck Reduction AnalysisModule 244 includes a Contralateral Analysis Module 276 in thisconstruction. Intertrochanteric Reduction Analysis and Femoral NeckReduction Analysis are described in combination with FIGS. 23-38 below.

Distal Radius Fracture Reduction Analysis Module 246 includesContralateral Analysis Module 278 in this construction. Distal RadiusFracture Reduction is described in relation to FIGS. 39-51 below.

Three aspects of the present invention are represented by FIGS. 4F-4Hfor intraoperative rescaling, intraoperative analysis, and AP Pelvisreconstruction, respectively. FIG. 4F is a schematic diagram of theIntraoperative Rescaling Module 218, FIG. 4C, with Image Input Module210 which contains Templated Input Module 201 a, Direct MeasurementRecording Module 203, Image Rescaling Module 205, and Template ObjectRe-rendering Module 207. A digital representation of a prosthesis,referred to as a “template”, is provided to Template Input Module 201 inone construction and, in another construction, is generated by thatModule 201. The digital template is provided to Direct MeasurementRecording Module 203, which also records a direct measurement such asthe width of the femoral head in one construction and, in anotherconstruction, utilizes a known implant dimension such as the width of ascrew or the radius of the acetabular component of a hip prosthesis. TheImage Rescaling Module 205 calculates possible adjustments in sizingthat may be required. For example, if a first image of a hip depicted afemoral head as having a width of 48 mm, but direct measurement bycalipers reveals that the true dimension is 50 mm, then the 2 mmdiscrepancy represents a four percent difference or deviation, and thefirst image is rescaled by four percent accordingly.

In some constructions, Re-rendering Module 207 includes a ProstheticPlacement Update Module 280 and/or, in certain constructions, an OtherObject Placement Update Module 282 to re-render objects other thanprostheses. Prosthetic Placement Update Module typically utilizescoordinate information, referred to herein as ‘centroid’ information,that is stored in a database and tells the system what reference pointshould remain stationary, relative to the image, during the rescalingprocess. Optionally, Intraoperative Rescaling Module 218 furtherincludes a Stationary Base Identification Module 2110 and a SecondaryImage Rescaling Module 2112, both shown in phantom, which can providerescaling of the secondary image to Templated Object Re-rendering Module207. These phantom modules facilitate the scaling of a second imagebased on directly observable measurements in the first image, if bothimages include a stationary base that identify the same anatomic points.More specifically, the first image is scaled directly via the DirectMeasurement Recording Module 203, but this scaling is then applied tothe second image by using the length ratios between the stable basesidentified in Stationary Base Identification Module 2110.

An alternative Intraoperative Analysis System 208′, FIG. 4G, includes anImage Capture Module 209, a User Data Input Module 211, and an AnalysisModule 213. Optional additional capabilities include a MathematicalCorrection Input Module 215 and an Error Analysis Module 217 asdescribed in more detail below. Image Capture Module 209 preferablyincludes at least one of a Camera Picture input 219 for receiving orotherwise acquiring at least one photograph, a Radiographic Image input221 for accessing a radiographic image from storage media or otherlocation, and an Interface 223 which communicates with a fluoroscope orother medical imaging device to capture, receive or otherwise acquire animage in real time. At least one of inputs 219, 221 and/or 223 capturesor otherwise acquires (i) at least one preoperative or contralateralreference image and (ii) at least one intraoperative or postoperativeresults image. The at least two images are provided to User Input DataModule 211 which utilizes a Stable Base Identification Module 225 toguide a user to select at least two stable base points, such as pointson a pelvis, to generate a stable base on each image, and a LandmarkIdentification Module 227 to prompt the user to select a location spacedfrom and separate from the stable base, such as a location on thegreater trochanter, on each image. Optionally, in certain constructionsthe Image Capture Module 209 also provides the images to the ErrorAnalysis Module 217, which guides a user to select at least one point onthe bony anatomy which contains the stable base points, to be analyzedfor anatomical or imaging inconsistencies that could create error in theAnalysis Module 213. An example of the operation of Error AnalysisModule 217 is illustrated in FIG. 70 below, where the difference betweentwo overlaid triangles, representing sets of three points in each imagealong the bony pelvis, is analyzed for pelvic alignment inconsistencies.These images with selected identifications are provided to the AnalysisModule 213 which utilizes at least one of the following modules in thisconstruction: Overlay Module 229 which utilizes visual analysis by theuser and/or an image recognition program; Mathematical Analysis Module231 which performs math calculations; or Other Analysis Module 233 whichutilizes different visual change criteria or quantification analysis.

If anatomy of the patient being analyzed shifts or otherwise movesbetween capture of the at least two images, then optional MathematicalCorrection Input Module 215 is beneficial to compensate for suchmovement. Hip Analysis Correction Module 235 is useful for hip surgery,such as by utilizing user identification of the femoral longitudinalaxis in each image, while Other Mathematical Correction Modules 237 areutilized as appropriate for other anatomical regions of a patientundergoing surgery or other corrective treatment.

An alternative AP Pelvis Reconstruction System 260′, FIG. 4H, utilizesImage Capture 239 to obtain an image of each side of a patient, such asboth sides of a hip, both shoulders, or two images of other anatomy forwhich two locations are substantially symmetrical or otherwisecomparable. The at least two images are provided to Image Scaling Module241 and Image. Stitching Location Capture Module 243, which identifiescorresponding locations such as the tip of the pubic symphysis in eachimage. After scaling and location identification by Modules 241 and 243,the images updated with that information are provided to Image StitchingModule 245 which generates an overlay as described in more detail below.

Optional modules include Contralateral Image Flipping Module 247 whichreverses one of the images before it is provided directly to ImageStitching Module 245, or is provided indirectly via one or both of ImageScaling Module 241 and/or Image Stitching Location Capture Module 243.The output of a larger, stitched, overlay-type image from ImageStitching Module 245 can be provided directly to an AP Pelvis AnalysisModule 251 or via an Image Cropping Module 249 to adjust the viewingarea of the stitched image. In this construction, Analysis Module 251includes one or more of Leg Length Analysis Module 253, Acetabular CupAngle Analysis Module 255, and Other AP Pelvis Analysis Modules.

Flowchart A, FIG. 5, depicts the operation of Intraoperative Rescalingin one construction of the system and method according to the presentinvention related to hip surgery. The operation is initiated, asrepresented by “Start” in step 300, and the femoral head is extractedand measured using calipers, step 302. The technique proceeds to step304, and a line is drawn in software corresponding to femoral headmeasurement such as illustrated in FIG. 2 above. The caliper measurementis recorded, step 306, FIG. 5, and the system calculates intraoperativerescaling from directly measured information, step 308. The systemapplies rescaling to the selected image, step 310, and, in oneconstruction, uses prosthetic centroid information and rescaling data toupdate location of the prosthesis on the image. More generally, thesystem utilizes at least one selected point, such as the mid-point ofthe trunion, that is associated with the prosthetic template to identifywhere the prosthesis should remain stationary on the rescaled image. Thesystem rescales and redraws all other objects on the image, step 314,and rescaling is concluded, step 316.

Flowchart B, FIG. 6, illustrates an Anterior Approach for hip surgeryutilizing Flowcharts G and J. This technique is commenced, step 320, andthe decision whether to conduct ipsilateral analysis is made, step 322.If yes, Flowchart G is initiated, step 324; if no, then a decision ismade whether to conduct Contralateral analysis, step 326. If yes, thenFlowchart G is utilized, step 328, after which it is decided whether tocreate and analyze stitched AP Pelvis, step 330. If yes, then FlowchartJ is activated. The Anterior Approach is concluded, step 334.

Flowchart G, FIG. 7, shows technique flow for both contralateral andipsilateral analysis. This technique is commenced, step 340, and eithercontralateral or ipsilateral analysis is selected, step 342. Forcontralateral analysis, the contralateral hip image is captured, step344, and the image is flipped, step 346. For ipsilateral analysis, thepreoperative ipsilateral hip image is opened, step 348. For both typesof analysis, Flowchart W is applied, step 350.

Flowchart W, FIG. 8, after being activated by step 350, FIG. 7, guides auser to identify a femoral landmark such as the greater trochanter instep 370, FIG. 8, and then the femoral axis is identified, step 372.These steps are illustrated in FIGS. 9 and 10, below. A line is thendrawn across the bony pelvis, step 374, as shown in FIG. 11.

The technique proceeds to capturing an operative hip image, step 352,FIG. 7, and identifying an acetabular component, step 354, such as shownin FIG. 12 below. Acetabular components are also shown in and discussedrelative to FIGS. 52-53 and FIGS. 55-59 below. The image is scaled byentering the size of the acetabular component, step 356, and Flowchart Wis then applied to the operative hip, step 358. The operative andcomparative hip images are scaled by a stationary base generated byselecting at least two reference points on the bony pelvis, step 360,such as shown in FIG. 15. The scaled images are then overlaid in step362 using the bony pelvis points, such as the overlaid lines 386 and 412shown in FIG. 16. Differences in offset and leg length are calculated,step 364, and the technique is terminated, step 366, returning to step326, FIG. 6, for ipsilateral comparison or to step 330 for contralateralcomparison.

Leg displacement is calculated in the pre-operation and post-operation(intra-operation) to give users a visualization of the operationprocess. The following steps 1-6 with Equations 6-10 are utilized in oneconstruction:

1. Draw a landmark, such as a single point or dot to represent a featuresuch as the greater trochanter, and a “stationary base” generated byselecting at least two points on the bony pelvis in each of the pre-opimage and post-op x-ray image.2. One procedure for aligning two images utilizing correspondingstationary bases, each base comprised of precisely two points thatdefine a line, is accomplished by the following approach. Based on thepositions of zero coordinate in each x-ray image, translate the linesegment position into screen coordinate system. P_(origional) is thepoint's coordinate on each image's coordinate plane. Z_(screen) is thecoordinate of zero in each image on the screen coordinate plane.

P _(screen) =P _(original) +Z _(screen)  EQ. 6

3. Find the rotation angle θ between the two line segment line_(postop)and line_(preop) are the line vector of each line segment.

$\begin{matrix}{\theta = {\cos^{- 1}\frac{{\langle{{line}_{postop} \cdot {line}_{preop}}\rangle}}{{{line}_{preop}}{{line}_{preop}}}}} & {{EQ}.\mspace{14mu} 7}\end{matrix}$

4. Calculate the rotation matrix R and apply it to the landmark inpre-op image. lm_(preop) is the center point position of landmark,lm′_(preop) is the center point position of landmark after rotation.

$\begin{matrix}{{R = \begin{pmatrix}{\cos \; \theta} & {\sin \; \theta} \\{\sin \; \theta} & {{- \cos}\; \theta}\end{pmatrix}}{{lm}_{preop}^{\prime} = {R*{lm}_{preop}}}} & {{EQ}.\mspace{14mu} 8}\end{matrix}$

5. Calculate the length ratio S between the two line segments and scalethe pre-op image based on it to get the landmark position after scaling.Use of more than two points for a stationary base benefits from a ‘bestfit model’ approach, such as an algorithm that minimizes the distancebetween respective points in each of the images.

S=length _(postop)/length_(preop)

lm″ _(preop) =S*lm′ _(preop)  EQ. 9

6. Finally, calculate the distance of the two landmark in bothhorizontal and vertical direction, visualize the results along with thetwo overlaid x-ray images.

{offset,leg length}=lm _(postop) −lm″ _(preop)  EQ. 10

A currently preferred implementation of the JointPoint IntraOp™ Anteriorsystem, which provides the basis for intraoperative analysis of theanterior approach to hip surgery, is illustrated in relation to FIGS.9-22. FIG. 9 is an image 376 of the right side of a patient's hip priorto an operation and showing a marker 378, bracketed by reference squares377 and 379, placed by a user as guided by the system, or placedautomatically via image recognition, on the greater trochanter as alandmark or reference point, such as indicated in box 224, FIG. 4D andin box 227, FIG. 4G, for the Landmark Identification Module of systems208 and 208′, respectively. FIG. 10 is an image 376′ similar to FIG. 9showing a reference line 380, bracketed by reference squares 381, 382,383 and 384, drawn on (i) the pre-operative, ipsilateral femur or (ii)the contra-lateral femur, to represent the longitudinal axis of thefemur. FIG. 11 is an image 376″ similar to FIG. 10 with a line 386,defined by two end-points, which is drawn across the pelvic boneintersecting selected anatomical features.

FIG. 12 is a schematic screen view of two images, the left-hand image376′ representing a pre-operative view similar to FIG. 10 and theright-hand image 390 representing an intra-operative view with a circle392 placed around the acetabular component 394 of an implant 398 toenable rescaling of that image. In some constructions, circle 392 isplaced by an image recognition program and then manually adjusted by auser as desired. Reference square 398 designates implant 398 to theuser. FIG. 13 is a schematic screen view similar to FIG. 12 indicatingmarking of the greater trochanter of the right-hand, intra-operativeimage 390′ as a femoral landmark 400, guided by reference squares 402and 404. FIG. 14 is a schematic screen view similar to FIG. 13 with areference line 406 drawn on the intra-operative femur in the right-handview 390″, guided by reference squares 407, 408, 409 and 410.

FIG. 15 is an image similar to FIGS. 11 and 14 with a line 386, 412drawn across the obturator foremen in both pre- and intra-operativeviews 376″ and 390′″, respectively. Reference squares 413, 414, 415 and416 guide the user while drawing reference line 412.

FIG. 16 is an overlay image showing the right-hand, intra-operative,PostOp image 390′″ of FIG. 15 superimposed and aligned with theleft-hand, pre-operative PreOp image 376″. In this construction, softbutton icons for selectively changing PreOp image 376″ and/or PostOpimage 390′″ are provided at the lower left-hand portion of the screen.

In another construction, more than two points are generated for thestationary base for each image, such as illustrated in FIG. 52 for apreoperative image 1200 and a postoperative image 1201, and in FIG. 53for a combined overlay image 1298 of the preoperative image 1200 and thepostoperative image 1201 of FIG. 52. Similar locations on the pelvis ineach image are selected to generate the points utilized to establish astationary base for each image. In image 1200, for example, a firstpoint 1202 is generated on an upper corner of the obturator foramen orat the pelvic tear drop, a second point 1204 is generated at the top orsuperior portion of the pubic symphysis, and a third point 1206 isgenerated at the lowest or inferior point on the ischial tuberosity.Lines 1208, 1210 and 1212 are drawn connecting those points to generatea visible stationary base triangle 1216 on image 1200. Also shown is apoint 1214 on the greater trochanter. In postoperative image 1201, firstand second points 1203 and 1205 correspond with first and second points1202 and 1204 in image 1200. A third point 1207 is shown in image 1201between reference squares 1209 and 1211 in the process of a userselecting the lowest point on the ischial tuberosity to correspond withthird point 1206 in image 1200. The user is prompted by “Mark lowestpoint on Ischial Tuberosity” in the upper portion of image 1201. Alsoshown is a circle 1213 around the acetabular component and a point 1215on the greater trochanter.

Establishing at least three points is especially useful for determiningrotational differences between images. Overlay image 1298, FIG. 53,shows the three points 1202, 1204 and 1206 of preop image 1200, formingthe visible preop stationary base triangle 1216, which is positionedrelative to the corresponding three points 1203, 1205 and 1207 of postopimage 1201, forming a visible postop stationary base triangle 1311overlaid relative to triangle 1216 in FIG. 53. A ‘best fit overlay’ canbe created using these points by identifying the centroid of the polygoncreated by these point, and rotating the set of point relative to oneanother to minimize the summation of distance between each of therelated points. In this construction, scaling of the two images may beperformed by these same set of points or, alternatively, a separate setof two or more points may be utilized to scale the two images relativeto each other. Clicking on a PreOp soft-button icon 1300 and a PostOpicon 1301 enable a user to alter positioning of images 1200 and 1201,respectively, within image 1298 in a toggle-switch-type manner toselectively activate or de-activate manipulation of the selectedfeature. One or more points of a stationary base may be shared withpoints establishing a scaling line. Preferably, at least one landmark isselected that is spaced from the stationary base points to increaseaccuracy of overlaying and/or comparing images.

Also illustrated in FIG. 53 are “Offset and Leg Length Changes” with“Leg Length: −0.2 mm”, “Offset: 21.8 mm” and “Confidence Score: 8.1”. Aconfidence ratio that describes the quality of fit can be created bycomparing the overlay area of the two triangles relative to the size ofthe overall polygon formed by the two triangles, including thenon-overlapping areas of each triangle. Abduction angle and anteversioncalculations are described below in relation to FIGS. 55-59.

A screen 420 viewable by a user during a surgical procedure guided by aJointPoint™ IntraOp Anterior™ system according to the present inventionis represented by FIG. 17. The user selects OVERLAY-IPSILATERAL HIP 422or OVERLAY-CONTRALATERAL HIP 424 with the option to use an existingoverlay. The operative hip side to be “replaced” is selected, via window426, to confirm which will be the operative side and the comparativeside; the comparative side is the same side as the operative side when aprior ipsilateral image is chosen. Another option for the user is toselect AP (Anterior-Posterior) Pelvis simulation, step 425; in anotherconstruction, AP Pelvis is presented to a user at a later stage withinContralateral Hip overlay creation.

Flowchart J, FIG. 18, presents one technique according to the presentinvention for AP Pelvis Stitching and Analysis. The technique iscommenced, step 500, and a contralateral image is flipped to itsoriginal orientation, step 502. A stitching line is drawn in theoperative image, step 504, such as a line 516 on the pubic symphysisshown in FIG. 19 for image 515, guided by reference squares 517, 518,519 and 520. A similar line is drawn on the contralateral image, step506, such as shown by line 522 in FIG. 20 for image 521, guided byreference squares 523, 524, 525 and 526. The images are stitched, step508, to simulate an AP Pelvis image as shown in FIG. 21 with overlappedstitching lines 516 and 522, with optional user adjustment by touchingmovement control icon 527, also referred to as a “rotation handle”. Theimages are cropped, step 510, and the simulated AP Pelvis is utilizedfor intraoperative analysis, step 512, such as leg length analysis oracetabular cobb angle. The technique terminates, step 514, and returnsto step 334, FIG. 6, in one construction.

FIG. 22 is view similar to FIG. 21 with one reference line 530 drawnacross the acetabular component of the image 521′, as guided byreference squares 531, 532, 533 and 534, and another reference line 536,as guided by reference squares 537, 538, 539 and 540, touching the lowerportions of the pelvis to enable accurate stitching for intraoperativeanalysis, including acetabular component cobb angle determination,according to the present invention. Additional analysis of theacetabular component, such as anteversion or other alterations ofposition, orientation or size, can be utilized as well.

Flowchart L, FIG. 23, illustrates Intraoperative Guidance forIntertrochanteric Reduction and Femoral Neck Fractures according toanother aspect of the present invention, referencing Flowcharts M and N.The technique begins, step 600, and reduction guidance is considered,step 602. If selected, then the procedure outlined in Flowchart M isinitiated, step 604. Otherwise, or after the Flowchart M procedure hasbeen completed, the technique proceeds to step 606 where the type ofsurgical procedure is selected. In this construction, for Femoral NeckFracture Reduction, the technique proceeds to step 612 to generate areport and store data for future reference. If IntertrochantericReduction is selected, then guidance for Apex-Tip calculation isconsidered. If selected, then the procedure described by Flowchart N isfollowed, step 610. Otherwise, or after the Flowchart N procedure hasbeen completed, the technique proceeds to step 612 where a report isgenerated and data stored as mentioned above. Guidance for thoseprocedures then ends, step 614.

Flowchart M, FIG. 24, for Intertrochanteric Reduction Guidance,commences at step 620 when selected and the technique proceeds to step622 where a contralateral hip image is taken and then flipped, step 624,to achieve a screen view such as illustrated in FIG. 26. The invertedcontralateral image is then processed as outlined in Flowchart P asdescribed below. The surgeon then reduces the hip fracture, step 628,and the user of this Guidance takes an X-ray-type image of the operativehip, indicated in step 630 as “User takes ipsilateral hip fluoro”. Thatimage is then processed by the procedure of Flowchart P, step 632, andthe contralateral and ipsilateral images are overlaid, step 634, such asshown in FIG. 32.

The overlay and neck shaft angles are analyzed in step 636, FIG. 24 and,if not acceptable, the procedure returns to step 628 for another roundof fracture reduction and analysis. Once acceptable, the procedure ofFlowchart M is ended, step 638, and the technique returns to step 606,FIG. 23 as discussed above.

Flowchart P, FIG. 25, for processing a Contralateral or IpsilateralImage, begins at step 640 and then at least one femoral landmark isidentified, step 642, such as marking the lesser trochanter with mark660 as shown in FIG. 26 for an inverted image 661 of the normal,un-injured contralateral side of the patient. A stationary basereference, preferably established by at least two points, such as forline 662, is drawn on the pelvis, step 644, FIG. 25, as shown in FIG. 27for image 661′. The neck shaft angle 663 is measured, step 646, as shownin FIG. 28 as 138 degrees for image 661″. Typically, this step 646, FIG.25, includes identifying the longitudinal axis 664 of the femur, FIG.28, because the femoral line 664 serves as one “leg” of the angle 663 tobe measured, with the other leg 666 established by the longitudinal axisof the femoral head. In some constructions, the femoral line 664provides an important reference relative to the stationary base 662 sothat the present system and method can compensate for any difference inleg positions between images. It is not unusual for a leg to shift itsorientation by 5 degrees to 15 degrees even when the leg is held intraction.

If scaling is desired, step 648, FIG. 25, then it is considered whethera scaling object is present in the image, step 650. If yes, then thescaling object is identified, step 652, and the object size is entered,step 654. After those steps 652-654 are completed, or if no scalingobject is found in step 650, the technique proceeds to the optional stepof drawing a femoral line, step 656 shown in phantom, if additionalanalysis is desired beyond measuring the neck shaft angle in step 646 asdescribed above. In any event, after the procedure of Flowchart P iscompleted, step 658, the technique returns to step 628 or step 634, FIG.24, in this construction.

FIG. 29 is a screen view with the left-hand image 661″ similar to FIG.28 and a right-hand image 670 of the fractured side of the patient,showing marking of the lesser trochanter on the fractured side with amark 672. FIG. 30 is a view similar to FIG. 29 showing marking of theobturator foramen of the fractured side with stable base line 674 inimage 670′. FIG. 31 is a view similar to FIG. 30 showing measurement ofneck shaft angle of 123 degrees on the fractured side as determined bymeasuring angle 676 between femoral axis 678 and femoral head axis 679.FIG. 32 is a combined image showing the fractured side image 670″overlaid on the normal, inverted side image 661″. Stable base lines 662and 674 are overlapped exactly in this construction.

Flowchart N, FIG. 33, shows scaling and measurement for APEX TIPcalculation as referenced in Flowchart L, step 610, FIG. 23. Thetechnique begins, step 700, and a fixation screw is inserted, step 702.An AP (Anterior-Posterior) X-ray-type photo is taken, step 704, and theAP image is scaled, step 706, by measuring the length or width of thescrew as shown in FIG. 34 or by measuring another object of known size.The Tip-Apex distance is measured, step 708, such as shown in FIG. 35. Alateral X-ray-type image is taken, step 710, and the lateral image isscaled, step 712, by measuring the screw as shown in the right-handimage of FIG. 36; alternatively, another object of known size ismeasured in the image and compared to the known measurement. TheTip-Apex distance is measured, step 714, in the lateral image such asshown in FIG. 37. AP and lateral Tip-Apex distances are calculated, step716, and the results are displayed such as shown in FIG. 38. If themeasurement is not satisfactory, step 718, then the technique returns inone construction to step 704 where replacement x-ray-type photos aretaken and reanalyzed. Alternatively, or if re-analysis still does notreveal acceptable measurements, the surgeon repositions the screw as analternative to step 702, and then the guidance resumes with step 704.Once acceptable, the procedure concludes, step 720, and the techniquereturns to step 612, FIG. 23.

FIG. 34 represents a screen view 730 of an image of a screw 732implanted through an implant 734 to treat an intertrochanteric hipfracture, showing measurement of the screw 732 with a longitudinal axisor length line 736, guided by reference squares 737, 738, 739 and 740generated by the present system in this construction. FIG. 35 is a view730′ similar to FIG. 34 showing measurement of Tip-Apex distance 742 of8.2 mm, guided by reference squares 743, 744, 745 and 746. FIG. 36 is aview 730′ similar to FIG. 35 plus a lateral view 750 on the right-handside of the screen, showing measurement of the width of the screw 732with line 752, guided by reference squares 753, 754, 755 and 756. FIG.37 is a view similar to FIG. 36 showing measurement of Tip-Apex distancein the right-hand image 750′ with a Tip-Apex line 762 of 3.6 mm, guidedby reference squares 763, 764, 765 and 766. FIG. 38 is a combined“Intertroch” view 770 showing both Tip-Apex Analysis and Neck ShaftAnalysis. The Lateral Tip Apex measurement of 3.6 mm from view 750′ isadded to the AP Tip Apex measurement of 8.2 mm from view 730′ tocalculate a Combined Distance of 11.8 mm in this example. An overlay 780of normal view 782 and fractured view 784 enables visual comparison, aswell as image recognition and analysis, to calculate a Fractured NeckShaft Angle of 123 degrees and a Normal Neck Shaft Angle of 133 degrees.

Guidance according to the present invention can be provided for otheranatomical regions such as wrists-hands, ankles-feet, and spinalanatomy. Flowchart Q, FIG. 39, provides Intraoperative Guidance forDistal Radius Fracture Reduction in wrists according to another aspectof the present invention, referencing Flowcharts R and S. This procedurebegins, step 800, and a choice is made whether to use radial inclinationand length for reduction guidance, step 802. If yes, the procedureoutlined in Flowchart R is followed, step 804. Once completed, or ifthose features are not selected at step 802, then use of Palmar slopefor reduction guidance is considered at step 806. If selected, theprocedure summarized by Flowchart S is followed, step 808. Aftercompletion, or if Palmar slope is not selected at step 806, then areport is generated and data stored, step 810. If the radial fracturereduction is not satisfactory, additional reduction is performed on theaffected wrist, step 814, and the technique returns to step 802. Oncesatisfactory, the procedure ends, step 816.

Flowchart R, FIG. 40, illustrates Radial Inclination and LengthReduction Guidance. An AP (Anterior-Posterior) image of thecontralateral wrist is captured, step 822, and the contralateral imageis flipped or inverted, step 824. The flipped contralateral image isprocessed utilizing the procedure outlined in Flowchart T, step 826, andan AP image is captured, step 828, for the affected wrist on whichsurgery is to be performed. The affected wrist image is processedutilizing the Flowchart T procedure, step 830, and the images are scaledand overlaid, step 832, such as illustrated in FIG. 51. The affected andcontralateral wrist radial inclination angles are calculated forcomparison, step 836, and a decision whether to scale the images ismade, step 838. If yes, the affected and contralateral wrist radiallengths are calculated for comparison, step 840. After suchcalculations, or if not selected, the procedure ends, step 842, and thetechnique returns to step 806, FIG. 39.

Flowchart S, FIG. 41, depicts Palmar Slope Reduction Guidance. Thisprocedure begins, step 850, and an image of the contralateral, normalwrist is captured, step 852. The Palmar slope or tilt is measured, step854, such as shown in FIG. 46. A lateral image of the affected wrist iscaptured, step 856, and the Palmar slope of the affected wrist ismeasured, step 858, such as shown in FIG. 50. Data and images for theaffected and contralateral wrist are displayed, step 860, such as shownin FIG. 51. The procedure ends, step 862, and the technique returns tostep 810, FIG. 39.

Flowchart T, FIG. 42, shows identification of various anatomicalfeatures in the wrist and image processing. It commences, step 870, anda radial styloid is identified, step 872, such as shown in FIG. 44. Theulnar styloid is identified, step 874, and the ulnar articular surfaceof the radius is identified, step 876. The longitudinal axis of theradius is identified, step 878, such as shown in FIGS. 43 and 47 for thenormal and affected images, respectively.

A stationary base reference line is drawn across the carpal bones inthis construction, step 880, such as shown in FIG. 45. The radialinclination is calculated, step 882. If the image is to be scaled, step884, then at least one scaling object is identified, step 886, and theobject size is entered, step 888. Intraoperative scaling is applied tothe image, step 890, and radial length is calculated, step 892. Oncecompleted, or if scaling is not desired, the procedure ends, step 894,and the technique returns to steps 828 or 832 of FIG. 40 as appropriate.

FIG. 43 represents a screen view of an image 900 of a “normal” wrist ofa patient with a line 900 drawn on the radius to indicate its centralaxis, guided by reference squares 904, 906, 908 and 910. FIG. 44 is aview 900″ similar to FIG. 43 with marking of selected anatomical points:Radial Styloid 912, guided by reference squares 914 and 916; UlnarBorder of Radius 918, guided by reference squares 920 and 922; and UlnarStyloid 924, guided by reference squares 926 and 928. FIG. 45 is a view900″similar to FIG. 44 with a reference line 930 drawn across the carpalbones to provide a stationary base reference, as guided by referencesquares 932, 934, 936 and 938.

FIG. 46 is a view of an image 940 of the normal wrist rotated to drawPalmar Tilt with longitudinal reference line 942, guided by referencesquares 944 and 946, and lateral reference line 948, guided by referencesquares 950, 952, 954 and 956, with a calculated Tilt of 7 degrees inthis example.

FIG. 47 is a screen view with the left-hand image 900″ similar to FIG.45 and a right-hand image 960 of the fractured side of the patient,showing marking of the central axis 962 of the radius on the fracturedside, guided by reference squares 964, 966, 968 and 970. FIG. 48includes a screen view image 960′ similar to image 960, FIG. 47, showingmarking of anatomical points on the fractured side: Radial Styloid 972,guided by reference squares 974 and 976; Ulnar Border of Radius 982,guided by squares 984 and 986; and Ulnar Styloid 992, guided by squares994 and 996. FIG. 49 is a view 960″ similar to FIG. 48 with a referenceline 1000 drawn across the carpal bones on the fractured side, guided byreference squares 1002, 1004, 1006 and 1008. In this constructions, auser touches one of the squares with a finger or a mouse cursor, andutilizes the square, such as by ‘dragging’ it, to move a marker to adesired location. This enables manipulation without blocking thelocation of interest.

FIG. 50 is a screen view with the left-hand image 940′ similar to FIG.46 and a right-hand image 1010 of the fractured wrist rotated to drawPalmar Tilt with longitudinal reference line 1012, guided by referencesquares 1014 and 1016, and lateral reference line 1020, guided byreference squares 1022, 1024, 1026 and 1028, with a calculated Tilt of 3degrees in this example. FIG. 51 is a combined view as a Distal RadiusReport according to the present invention, after the fractured side hasbeen reduced, that is, after a surgical operation has been performed onthe fractured side. The “Normal” image is an inverted contralateralimage of the opposite wrist-bones of the patient. Although notillustrated, one or more plates or other implants may be utilized beforeand/or after analysis according to the present invention to reducefractures as part of the surgical procedures to restore orthopaedicfunctionality at the surgical site. Upper-left Image 1030 is an APOverlay of Radial Inclination to analyze radial bone fracture reductionwith specific regard to angle in AP orientation. Contralateral or‘Normal’ Radial Inclination is 2.4 degrees in this example and theFractured Radial Inclination is 10.5 degrees. Radial inclinationreference lines for the normal wrist-bones are shown in dashed lineswhile reference lines for the fractured wrist-bones are shown in solidlines. Preferably, an overlay line passing through the carpal bones inthe each of images is utilized as stationary bases to generate images1030 and 1050, although these overlay lines are not shown in images 1030and 1050. Lower-left Image 1040 is an AP image of Reduced Fracture,after reduction has been analyzed by the system, to confirm imagecapture for future reference and digital record-keeping.

Upper-right Image 1050 in FIG. 51 is an AP Overlay of Radial Length tocompare analysis of reduced radial bone location, with two sets 1052 and1054 of substantially parallel lines, also with dashed lines for Normaland solid lines for Fractured wrist-bones. The distance between the twosets 1053, 1054 of lines indicates radial length measurement. Radiallength lines are drawn using radial styloid and ulnar styloid locationinformation. The quality of the fracture reduction is thereby analyzed;changes in radial length may indicate an orthopaedic problem. Image 1050enables the user to visually inspect and analyze the quality of thefracture reduction and, therefore, numerical values are not provided inimage 1050 in this construction. Lower-right Image 1060 is a LateralView of Distal Radius Fracture after Reduction to provide Palmar Tiltanalysis that compares fractured Palmar Tilt angle of 3 degrees in thisexample to the contralateral or ‘Normal’ Palmar Tilt angle of 7 degrees,although only the fractured wrist-bones are shown in image 1060 in thisconstruction.

FIGS. 52 and 53 are described above.

In some constructions, a guidance system is provided to adjust theviewing area of one image on a screen to track actions made by a user toanother image on the screen, such as to focus or zoom in on selectedlandmarks in each image. This feature is also referred to as anautomatic ‘centering’ function: as a user moves a cursor to ‘mark’ afeature on one image, such as placing a point for a landmark or astationary base on an intraoperative image, the other image on thescreen is centered by the system to focus on identical points ofinterest so that both images on the screen are focused on the sameanatomical site. FIG. 54 is a schematic combined block diagram and flowchart of an identification guidance module 1400 utilized in oneconstruction to assist a user to select landmarks when comparing a post-or intra-operative results image, box 1402, with a reference image, box1404. The module is initiated with a Start 1401 and terminates with anEnd 1418. When a visual landmark is added to a post-operative image, box1406, the module 1400 locates all landmarks “1” on the pre-operativereference image, box 1408, and calculates the visible area “v” withinthe pre-operative image in which to scale, such as by using Equation 11:

v=[maxx(1)−minx(1),maxy(1)−miny(1)]  EQ.11

The identical landmark on the pre-operative image is located and itscenter-point “c” is determined, box 1410. The identical landmark on thepre-operative image is highlighted in one construction to increase itsvisual distinctiveness, box 1414. The pre-operative image is centered,box 1410, and scaled, box 1412, such as by utilizing the followingEquations 12 and 13, respectively:

Center=c−(v)(0.5)  EQ.12

Scale=i/v  EQ.13

The user manipulates one or more visual landmarks in the results image,box 1416, as desired and/or as appropriate. In some constructions, theuser manually ends the guidance activities, box 1418 and, in otherconstructions, the system automatically discontinues the guidancealgorithm.

In certain constructions, image recognition capabilities provide“automatic”, system-generated matching and alignment, with a reducedneed for user input. Currently utilized image recognition providesautomatic detection of selected items including: the spherical ballmarker frequently utilized in preoperative digital templating; theacetabular cup in digital templates and in trial prosthetics; and theCobb Angle line, also referred to as abduction angle.

Note that “PostOp” typically indicates post-insertion of a trialprosthesis during the surgical procedure, and is preferablyintra-operative. The PostOp image can also be taken and analysisconducted after a “final” prosthesis is implanted. “PreOp” designates animage preferably taken before any surgical incision is made at thesurgical site. In some situations, the image is taken at an earliertime, such as a prior visit to the medical facility and, in othersituations, especially in emergency rooms and other critical caresituations, the “PreOp” image is taken at the beginning of the surgicalprocedure. Ball markers BM are shown but are not utilized for alignmentbecause ball markers can move relative to the patient's anatomy. FurtherPreOp and PostOp icons are provided to adjust viewing features such ascontrast and transparency. Preferably, at least one icon enablesrotation in one construction and, in another construction, “swaps” theimages so that the underlying image becomes the overlying image.

In certain constructions, intraoperative analysis and guidance is alsoprovided to a user for one or more individual components of an implantsuch as an acetabular cup of a hip implant. System 1500, FIG. 55,analyzes the orientation, including abduction angle and anteversion, ofan acetabular cup in this construction. System 1500 includes ImageSelection Module 1502, Image Recognition Module 1504, LandmarkIdentification Module 1506, Acetabular Cup Bottom Identification Module1508 and Abduction Angle and Anteversion Calculation Module 1510 in thisconstruction, with system operation and technique described below inrelation to FIGS. 56-59.

FIG. 56 is an image 1520 of an acetabular cup 1522 positioned in theleft acetabulum of a patient with a circle 1524 drawn around its outerhemispherical surface to provide diameter information for the component.In some constructions, a user initiates component analysis by touching afinger or a stylus to the “Diameter Information” field 1532. At anytime, as described in relation to FIG. 59 below, the user preferably isable to return to a previous action such as by touching or clickinganother field 1532, for example “Mark Greater Trochanter”. In oneconstruction, an image recognition algorithm in Image Recognition Module1504 automatically operates to identify the acetabular cup 1522 in theimage 1520 of FIG. 56 and surround it with the circle 1524, bracketed bysmall guide dots 1526, 1528, as indicated by the prompt “Diameterinformation” 1532 at the top of image 1520. In some constructions, theguide dots or squares serve as “navigation handles” to enable the userto manipulate one or more features designated by the handles, such as bytouching or clicking and dragging the handles to move the designatedfeatures. This screen 1520 relates to step 1608 in flowchart X,algorithm 1600, FIG. 59 below. If the initial, auto-generated circle isnot acceptable, then the user manually adjusts the position and/or sizeof circle as appropriate, step 1610.

FIG. 57 is an image 1540 similar to that of FIG. 56 with two lines 1542and 1560 drawn to calculate abduction angle. The user accesses screen1540, having a heading or prompt 1541 of “Calculate Abduction Angle”,for example, to fit in the abduction angle landmarks for calculation.The terms “abduction” and “abduction angle” are also known as“inclination”. The “User positions neutral axis” step 1612 in flowchartX, FIG. 59 below relates to screen 1540, FIG. 57, in which neutral axisline 1560 is placed to touch the two ischial tuberosities of the pelvicgirdle. Guide squares 1562, 1564, 1566 and 1568 enable the user tomanipulate the neutral axis line 1560. Abduction angle line segment 1542is auto-positioned across circle 1524 using image recognition, step1614, FIG. 59, wherein the system automatically detects where theacetabular cup 1522 is positioned, FIG. 57, and the system places theline segment 1542 across the abduction angle on the cup as accurately asit can do so. The abduction line segment 1542 preferably is a diameterline of the circle; when segment 1542 is extended virtually by thesystem to intersect the neutral axis line 1560, the abduction angle isgenerated and measured at that intersection. In one construction, theabduction line defaults to about 45 degrees from the neutral line 1560until more accurate auto recognition occurs. The guide square “handles”1544, 1546, 1548 and 1550 around the abduction line segment 1542 enablethe user to rotate the abduction line segment 1542, but the abductionline continues to look like a diameter line so that it remains properlyaligned with the actual orientation of the acetabular cup 1522.

During the “User adjusts abduction angle manually if required”, step1616, FIG. 59, the user can use the navigation handles 1544, 1546, 1548and 1550, FIG. 57, after the image recognition has run, to make theabduction angle substantially perfect. In “System calculates anddisplays abduction angle”, step 1618, the neutral axis 1560 ismathematically compared to the abduction line segment 1542 to determinethe angle. In this construction, the abduction angle data of “32°”, forexample, is displayed in lower right field 1543 in FIG. 57.

If the user wants anteversion information, then at step 1620, FIG. 59,“YES” is selected and arcs 1572, 1574, FIG. 58, are positioned thatidentify the bottom of the acetabular component 1522 in step 1622. Thesystem then calculates and displays the anteversion angle, which relatesto the z-plane rotation of the acetabular component 1522. Some users mayonly want to use abduction angle data and will then skip anteversion atstep 1620 and proceed to step 1626 where it is decided whether to modifyplacement of the acetabular component intraoperatively. If “yes” isselected, then the algorithm proceeds as indicated by path 1628 tore-position the acetabular component, step 1604 et seq. Once the user issatisfied with the placement, then algorithm 1600 terminates, step 1630,and the system resumes from where step 1602 was initiated.

FIG. 58 is an image 1570 similar to that of FIG. 57 with arcs drawn atthe bottom of the acetabular cup 1522 to assist calculation ofanteversion in the z-plane. Image 1570 includes a vertically-oriented“slider control” 1580 in this construction, with vertical line 1582 anda movable setting knob 1584, to enable a user to easily increase ordecrease the size of arcs 1572 and 1574. Vertical slider control 1580increases or decrease the size of the arcs 1572, 1574. These arc lines1572, 1574 are mirror images of one another relative to the abductionline segment 1542 and are used to identify the location of the bottom ofthe cup 1522 in the image 1570. Sliding knob 1584 all the way to ‘0’will cause the arcs 1572, 1574 to overlay the abduction angle linesegment 1542. Sliding all the way to ‘100’ will cause the arcs tooverlay the existing circle 1524. This relates to “Arcs are positionedthat identify bottom of acetabular component”, step 1622, FIG. 59. Guidehandles 1569 and 1571, FIG. 58, are provided for at least one of arcs1572 and 1574 as described in relation to FIG. 59 below.

During the next step 1624, “System Calculates and Displays Anteversion”,any updates that are applied to the arcs 1572, 1574 via slider 1580 willlead to re-calculation and updated display of anteversion value such as“14°” in field 1594. Note how the guide handles 1573, 1575, 1577 and1579 in FIG. 58 allow the precise location of the abduction angle tostill be updated if required, via manipulation of abduction line segment1542, which is especially useful if the user continues positioning thearcs, to more closely achieve actual orientation values. Soft-buttonicons 1590 and 1592 for “Abduction Angle” and “Anteversion”,respectively illustrated with solid and dashed lines, serve as “toggles”when touched or clicked by a user to selectively activate which screenfeatures may be manipulated by the user. In one construction, thefunctionality of one or more of guide handles 1573, 1575, 1577 and/or1579 is altered according to which of icons 1590 and 1592 is selected,to adjust features relating to abduction and anteversion, respectively.

FIG. 59 is a flowchart of anteversion and abduction analysis by themodules of FIG. 55. Flowchart X, algorithm 1600, FIG. 59, is activatedwhen a user selects “Cup Check” icon or text to initiate cup analysis.In some constructions, this prompt will persist somewhere on thenavigation screen throughout the workflow. This is a ‘forked’ or loopworkflow which will start, step 1602, from wherever it is initiated andthen return to the same place upon finish of the fork. First action of“Position Acetabular Component”, step 1604, is conducted by a surgeon.The “acetabular component” in this situation of “pre-stem insertion”,can be a number of components: a standard acetabular cup, a reamer, or atrial acetabular cup. The actual component analyzed depends on what thesurgeon would like to have analyzed by the system according to thepresent invention.

After initial installation of a component, a prompt such as “Take imageof acetabular component”, step 1606, guides the user to take a pictureof an AP Pelvis view with implanted cup, such as illustrated in FIG. 56.Alternatively, a prompt of “Select from Library” or other guidance canbe provided to the user, in a manner similar to other techniquesdescribed above. Steps 1608-1616 are described above in relation toFIGS. 56-57 in which a circle is established around the acetabular cupand diameter information of the circle is generated.

Initiation of step 1618, FIG. 59, “System calculates and displaysabduction angle”, causes two lines to appear, the pelvic reference line1560 and abduction angle line segment 1542, FIG. 57, in a manner that issimilar to abduction angle analysis on simulated AP Pelvis describedabove. Pelvic reference line 1560 is also referred to as the “neutralaxis” line, step 1612. Alternatively, a “T” or other geometric shapeappears on the screen when a soft button “toggle” is activated. Thepelvic reference line 1560 is a line across image 1540, placed bydefault horizontally on image 1540 and approximately 75 percent of theway down the image (in a y-coordinate system). This is similar to theCobb Angle functionality discussed above.

For the abduction angle line, the user draws the line segment 1542 asprecisely as possible across the cup 1522. In some constructions, animage detection/recognition algorithm is provided to assist thisprocess. Abduction angle preferably is calculated in real time anddisplayed in this step. In one construction, the abduction anglecontinues to be displayed to the user throughout the additional steps inthis process. Determining the abduction angle is a straightforwardcalculation, calculated as the angle between the neutral axis 1560 andabduction line segment 1542, FIG. 57, similar to how it works in APPelvis reconstruction. When a user such as a surgeon wants to get returnto operating on the patient and not continue with anteversion, then theuser selects “No” in steps 1620 and 1626, FIG. 59, the system “saves”the calculated information, and returns to where algorithm 1600 wasinitiated while the surgeon resumes surgery on the patient.

For step 1622, the user works with two inner arcs to analyzeanteversion. The system keeps the acetabular component circle visiblefrom the earlier step, but it is now non-modifiable. The abduction linepreferably is removed from the visual display. Preferably the circleappears to be “paper thin” (and even slightly transparent) in thisscreen. End points 1526 and 1528, FIG. 57, are added on each side of thecircle 1524 where the abduction line 1542 transected the visual circle1524.

Now the system proceeds to modify the two arcs 1572 and 1574, FIG. 58,that are contained within the circle 1524. Each arc is on one of thesides of the abduction line segment 1542. These arcs are mirror imagesof one another relative to the abduction line. Each arc should defaultto a distance of 35% of the circle radius; for example, if the radius is28 mm (or 28 x pixels, whatever it may be, as scaling is not needed forthis process), the distance of the midpoint of the arc from theabduction line should be approx. 9 mm (or 9 x pixels). One of the arcs,such as the lower one 1574, has navigation controls or handles 1569 and1571 on it, or directly at the center of the arc 1574. The other arcwill move in tandem with this arc in a “captured” manner. Navigationcontrol for this object will be a slider control (similar to atransparency control, but longer and vertical). As described above forone construction, at a setting of 100 percent on the slider, the arcwill be directly on the cup, while at 0 percent on the slider, the arcwill be directly on the abduction angle line. Preferably an initialdefault setting of 35 percent is provided. Also preferably, the slidercontrol 1580 is movable on the screen, and is initially positioned bythe system in the middle of the screen.

Anteversion is calculated in real-time and displayed as arcs 1572 and1574 are modified. A larger display is desired for both abduction angleand anteversion. Anteversion is calculated in one construction accordingto Liaw et al., “A New Tool for Measuring Cup Orientation in Total HipArthroplasties from Plain Radiographs”, Clinical Orthopaedics andRelated Research No. 451, pp. 134-139 (2006) currently available at:http://www.csie.ntu.edu.tw/˜fuh/personal/ANewToolforMeasuringCupOrientation.pdf.

As described on Page 136 of the Liaw et al. article, FIG. 2-B showscalculation of ‘true anteversion’ angle: Point F is known, as themidpoint of the diameter line, and Point E can be identified from circlesurround the cup. The highest point on the cup is point E, which has thesame x-coordinate as Point F and a y-coordinate equal to (y coordinateof Point F+radius of circle diameter). Point G is a point on the ‘arc’horizontal from Point F. Angle Beta(t), which represents trueanteversion, can be calculated from this data.

Finally, the user can Capture/Save this analysis for later review andthen ‘Go Back’ to standard workflow. High Level Workflow FunctionalitySummary: preferably, the system provides the user with the ability toSave, Exit Cup Check, return to previous screen, and view after thefinal overlay. In some constructions, the system captures anteversion onthe reconstructed AP Pelvis as well, in addition to the abduction anglecalculation that already exists. A soft button with a designation suchas “Calculate Anteversion” is provided for the user to click or touch atthe end of ‘abduction angle’ process in simulated AP. If selected, thenprocess continues, else process stops.

In some techniques, the Abduction Angle can be altered if user decidesto keep a physical handle attached to the acetabular cup. The handlewill appear on an x-ray image or fluoro image, and can be used todetermine abduction. A perpendicular line to the cup handle line thatintersects the Ischial Tub line will produce a very accurate AbductionAngle. Finally in Flowchart X, FIG. 59, is the user satisfied with theresults? If not, the user can reposition the acetabular cup, retake afluoro shot, and begin the process again as shown in the flowchart.Thus, a software-controlled solution is achieved according to thepresent invention, anatomically disconnected from the patient, toprovide intraoperative data that improves clinical decision-makingduring surgery without increasing trauma to the patient.

In certain constructions, a system and method according to the presentinvention includes an inventive alternative methodology for analyzingintraoperative leg length and/or offset changes using a differentapplication of the stationary base, intraoperative scaling andanatomical landmark identification techniques. Referred to herein as‘Reverse Templating”, the system and method combines the use ofintraoperative data, gathered from intraoperative image analysis, withintraoperative templating on a preoperative ipsilateral image. Theprocess begins in some constructions by (1) acquiring preoperativeipsilateral and intraoperative images and (2) scaling and aligning theseimages by using identifiable features on the pelvis to serve as astationary base, together with intraoperative data of the acetabularcomponent. The system initially displays the preoperative andintraoperative images next to one another, with the system aligning andscaling the images relative to one another by using the identifiedstationary bases in each image. The absolute scale, that is, objectivescaling according to a measurement system such as in millimeters, atleast for the intraoperative image, is determined by visuallyidentifying the prosthetic implant device itself while entering theknown metric size for at least one dimension of the device. Both imagesare scaled in some constructions using their respective stationary basesand, in other constructions, each image is scaled independently, such asby using a ball marker for the preoperative image and the knowndimension of the implant for the intraoperative image.

In preferred implementations of this Reverse Templating method, the useris guided to identify one or more landmark points (i.e. the tear dropanatomical feature of the pelvis) on each image and is then guided bythe system to position templates that directly overlay the acetabularcomponent and femoral stem implants visible in the intraoperative image.In other words, a first, acetabular template is superimposed over theacetabular component and a second, femoral template is superimposed overthe femoral stem of the implant during certain preferred implementationsof the present overlay technique. This template overlay in theintraoperative image does not calculate any offset or leg length datadirectly, but it provides other intraoperative data (i.e. abductionangle) that enables the system and user to precisely position theacetabular component and femoral stem templates on the preoperativeimage. The use of intraoperative data in the preoperative image, asgathered from overlaying templates in the intraoperative image,transforms this approach from an “estimation” technique to one thatprovides extremely precise calculations of intraoperative offset and leglength changes. The technique's use of templates additionally allows thesurgeon to proactively analyse how intraoperative changes to implantselection will affect leg length and offset.

One system that implements this intraoperative Reverse Templatingtechnique is shown in Intra-operative Analysis Module 1850 in FIG. 67.The method for one construction of the system is depicted in flowchartsegments 1870 and 1872, FIGS. 68A and 68B, that comprise a Flowchart Udepicting Intraoperative Templating Flow. The system and method thatimplements this Intraoperative Templating technique generates imagessuch as shown in FIGS. 60-66.

In one construction, intra-operative Analysis Module 1850 according tothe present invention, FIG. 67, includes Image Selection Module 1852which communicates with a Rotation and Scaling Module 1860 thatpreferably includes an optional Stable Base Identification Module 1854,shown in phantom. In this construction, Template Input Module 1852further communicates with an optional Longitudinal Axis IdentificationModule 1856, shown in phantom, that provides femoral axis identificationin this construction which is particularly useful if the first andsecond images are not taken in virtually the same position, that is,along the same viewing angle, and a Landmark Identification Module 1858.All three of modules 1860, 1856 and 1858 provide inputs toIntraoperative Template Placement Module 1862; in this construction,Stable Base Identification Module 1854 generates a stable base, alsoreferred to as a stationary base formed from two or more points selectedon a patient's anatomy, as part of Rotation and Scaling Module 1860,whose results are then provided to Intraoperative Template PlacementModule 1862. In one construction, Module 1862 facilitates placement ofdigital templates of acetabular and femoral components onto apreoperative image using intraoperative data including templating datafrom the intraoperative image. After templating, information is providedto the Differential Analysis Module 1864 for further calculations andanalysis, including offset and leg length calculations in someconstructions. One or more of the modules 1852-1864 can interface with adisplay or other interactive communication with a user. Another optionalcomponent is an Intraoperative Templating Module 1863, shown in phantom,which provides further processing of the output of IntraoperativeTemplate Placement Module 1862, such as performing “what if” planninganalysis or to modify one or more of the digital templates, beforeproviding the results to Differential Analysis Module 1864.

All references to “module” in relation to FIGS. 68A-69 refers to themodules of Intraoperative Analysis Module 1850, FIG. 67, with “ID”referring to “Identification”. Further, the order in which thepreoperative, reference image and the intraoperative, results image aremarked or scaled among steps 1876 to 1902 can be interchanged in otherimplementations. In other alternative constructions, analysis isconducted utilizing a contra-lateral image instead of or in addition toan ipsa-lateral image as described below.

The method begins in one construction with initiation, step 1874, FIG.68A, and a user-selected preoperative ipsilateral hip image is openedfor display, step 1876, by Image Selection Module 1852. The systemguides the user to indicate whether the image is a right or left hip. Ascreen view 1700, FIG. 60, depicts the selected image 1702 of the rightside of a patient's hip prior to an operation, with pubic symphysis PS,obturator foramen OF and right femur F_(R). The image 1702 can beacquired by directly interfacing with an imaging system or otherwise bytaking a picture of a radiographic image using an iPhone camera orsimilar technology. A label 1718 of “PreOp” indicates that it is apre-operative image.

The method continues with the preoperative hip image being processed,step 1878, by the technique of flowchart 1880, FIG. 69, which is aFlowchart Y showing functions applied to the pre-operative hip image forIntraoperative Templating of Flowchart U. The specific functions includeidentification of a ‘stable base’ (sometimes referred to as a‘stationary base’) according to the present invention, identification ofthe femoral axis, and identification of the greater trochanter in thisconstruction. At step 1882, FIG. 69, a reference line is drawn by theStable Base ID Module 1854 across the bony pelvis, as illustrated by the“stable base” line 1704 in FIG. 60 which is shown extending from theteardrop TD to the lower portion of the pubic symphysis PS. A femoralaxis line 1706, representing the longitudinal axis of the femur, is thenidentified in step 1884, FIG. 69, by the Longitudinal Axis ID Module1856. A femoral landmark such as the greater trochanter is identified,step 1886, by Landmark ID Module 1858; in other constructions, one ormore alternative femoral landmarks such as the lesser trochanter areidentified. As guided by step 1886, guide squares 1710 and 1712, FIG.60, assist the user in placing a marker 1714 on the greater trochanterGT as a landmark or reference point. In some constructions, the “stablebase” line 1704, “femoral axis” line 1706, and marker 1714 on thegreater trochanter (or other femoral landmark) may be automaticallyplaced in appropriate locations by the system's image recognitioncapabilities and then may be modified by the user. In otherconstructions, the user is prompted to place these lines and markerswithout system intervention.

Continuing with step 1890, FIG. 68A, the technique captures theoperative hip image, that is, an image is obtained of the patient's hipduring surgery, utilizing the Image Selection Module 1852. The operativehip image may be captured through various methods, such as through adirect connection with a fluoroscopy machine, a DICOM file upload, or bythe user taking a camera picture of the radiographic image using an iPador other mobile computing device. After capturing the operative hipimage, the acetabular component is identified in step 1892 by theRotation and Scaling Module 1860, such as shown in FIG. 61. Theintraoperative image is scaled, step 1894, by entering the size of theacetabular component into the system, which is processed by Rotation andScaling Module 1860.

FIG. 61 represents a screen 1720 viewable by the user during a surgicalprocedure guided according to the present invention showing two imagesin split screen view, the left-hand image 1702′ representing apre-operative view similar to FIG. 60, and the right-hand image 1722representing an intra-operative view with a circle 1724 placed aroundthe acetabular component 1730 of an implant 1732 to enable rescaling ofthat image. In some constructions, the system attempts to automaticallyplace the circle 1724 around the acetabular component 1730 using imagerecognition algorithms. In other constructions, the user is prompted toplace the circle around the acetabular component without systemguidance. The user may use guide squares 1726 and 1728, if required, toalter the size and position of circle 1724 so that it preciselyencircles the acetabular component 1730. In one construction, the userenters the diameter of circle 1724, such as “54 mm”, using data entrybox 1727. This enables the system to generate absolute scaling in theintraoperative image by taking the diameter in pixels of the acetabularcomponent and combining that with the known diameter in millimeters.Other prompts to guide the user include the choice of soft-key 1740 for“Use Ball Marker” and soft-key 1742 for “Use Ruler”, to allow the userto accomplish intraoperative scaling using other anatomical features orobservable devices if desired.

The method continues with step 1896, FIG. 68A, by applying Flowchart Y,FIG. 69, to the operative hip, including steps 1882-1886 as describedabove, in order to identify the “stable base”, “femoral axis” andgreater trochanter in the operative hip image, as illustrated in FIG.62. The shoulder of the femoral implant is identified, step 1898, in theintraop image by Landmark ID Module 1858, which is also illustrated inFIG. 62.

FIG. 62 is a schematic screen view 1750 similar to FIG. 61 withpre-operative image 1702″ and indicating placement of a mark 1760 of thelateral shoulder 1761 of the prosthesis 1732 of the right-hand,intra-operative image 1722′, as guided by guide squares 1762 and 1764.Also shown is the greater trochanter having mark 1756 as a femorallandmark and a stable base line 1754 connecting the tear drop TD to thelower portion of the pubic symphysis PS. Alternative constructions mayuse a stable base line 1754 that connects a different set of 2 or moreanatomical landmarks across the pelvis, but the landmarks must be placedon consistent points across the preoperative and intraoperative images.Similarly, alternative constructions may replace the greater trochanterwith a different femoral landmark (i.e. lesser trochanter) that can beidentified in both preoperative and intraoperative images. In someconstructions, the system will attempt to auto-generate placement of themark 1760 at the lateral should 1761 of the prosthesis, the mark 1756 onthe greater trochanter, and stable base 1754 across pelvic landmarks,and then allow the user to modify placement. Other constructions willprompt the user to determine placement of this data without automatedguidance.

The identification of consistent stationary bases in the preoperativeimage and intraoperative images can be combined with the absolutescaling data in the intraoperative image to apply absolute scaling tothe preoperative image. To accomplish this, the method continues in step1900, FIG. 68A, by scaling the preoperative image in pixels by Rotationand Scaling Module 1860, which scales the lines across the bony pelvisin both the preoperative and intraoperative images so that they are ofidentical size in pixels, such as by using stable base line 1704, FIG.61, and stable base line 1754, FIG. 62.

Continuing with step 1902, FIG. 68A, absolute scaling is applied to thepreoperative image by using the known size of the acetabular componentin the intraoperative image. Because both images are scaled according toan identical stationary base, the absolute scale ratio in theintraoperative image, determined by acetabular component diameter, canbe applied to the preoperative image. This unique technique providesprecise scaling to the preoperative image by using objects of known sizein the intraoperative image and applying this scaling to thepreoperative image. The result is that a significantly more preciseabsolute scaling can be determined in the preoperative image, ascompared to traditional preoperative image scaling techniques thatutilize ball markers or similar techniques.

Alternative constructions may alternatively apply absolute scaling tothe preoperative and intraoperative images directly in each image, andwithout the need for a stationary base. For example, each image may bescaled by a ball marker or other scaling device, known magnificationratios of a radiographic device, or direct measurements of anatomicalpoints (such as a direct measurement, via callipers, of the extractedfemoral head, which can be used to scale the preoperative image).

Alternative constructions may also replace the ‘stationary base’ withvarious other techniques that could be used to scale and align thepreoperative and intraoperative images relative to one another. Oneexample of such a construction would involve overlaying two images anddisplaying them with some transparency so that they could both be viewedon top of one another. The user would then be prompted to rotate andchange their sizing, so that the pelvic anatomy in the two images wereoverlaid as closely as possible.

A “side by side” display is generated by the Rotation and Scaling Module1860, step 1904, which is consistently rotated and scaled based on thestable base line across the bony pelvis. In some constructions, a singleimage that combines preoperative and intraoperative picture renderingsside by side will be displayed. Other constructions will maintain thepreoperative and intraoperative images as separate images. Allconstructions will rotate and scale the images relative to one anotherusing the stationary bases across the pelvis.

After aligning the preoperative and intraoperative images, the methodcontinues with step 1906, FIG. 68B, with the user or system drawing anacetabular cup template directly on top of the implant in theintraoperative image, such as shown in FIG. 63. The acetabular cuptemplate is placed to match the actual abduction angle by IntraoperativeTemplating Module 1862. FIG. 63 is a schematic screen view 1770 similarto FIG. 62 with a reference rectangle 1772, also referred to as a “box”or “frame”, indicating an acetabular component template 1774, with acentral point 1775, placed directly above the acetabular component ofthe prosthesis on the intra-operative femur in the right-hand view. Insome constructions, the system combines known anatomical data (i.e. thecircle 1724 placed around the acetabular component in FIG. 61) and imagerecognition to generate the initial placement of the acetabularcomponent template on the intraoperative image. In an alternativeconstruction, the acetabular component template is placed at a defaultabduction angle and modified by the user. In either construction, theuser can modify the template abduction angle to match the actualacetabular component abduction angle by using movement control icon1776, also referred to as a “rotation handle”, similar to the icon 527shown in FIG. 21 above. This assists “touch” or “click and drag” controlused to facilitate repositioning and adjustment of the template 1774relative to the image of the acetabular component 1730 of implant 1732.In one construction, icon 1777 is clicked or touched to “activate”rectangle 1772, template 1774 and/or movement control icon 1776 toenable movement thereof by the user. Additional information is providedto the user by fields 1778 such as “Size 54 mm”, “Type Standard”, and“Offset 0” as illustrated. Markers 1780 and 1782 have been placed inimages 1702′″ and 1722″, respectively, to designate the location of teardrop TD in each image. In some constructions, the system mayautomatically generate markers 1780 and 1782 because the teardrop TD hasalready been identified, for example in a situation when the teardrop isused to create a stationary base and can be readily identified.

In step 1908, FIG. 68B, the system positions the acetabular cup templatein identical position, relative to the pelvis, in the preoperative imageas compared to the placement on the intraoperative image describedabove. This is illustrated in FIG. 64 using known teardrop locations inthe pre- and intra-operative images.

FIG. 64 is a schematic screen view 1790 similar to FIG. 63 but with theacetabular template 1774′, with a central point 1775′, now re-positionedon top of the femoral head in the preoperative view 1792. The acetabulartemplate positioning in the preoperative image, as shown in this figure,is auto-generated by the system using intraoperative image data gatheredfrom the placement of the acetabular template in the intraoperativeimage. Specifically, the system calculates the x and y distances fromthe teardrop to the acetabular prosthesis in the intraoperative imagedisplay, and auto-generates the acetabular template position in thepreoperative image by maintaining the distance from the teardrop to theacetabular template in the preoperative image. The system also maintainsthe abduction angle obtained by maintaining the acetabular templateabduction angle that was analysed in the intraoperative image. Thisprocess ensures that the acetabular template is placed in thepreoperative image in a position, relative to the pelvis, that preciselymatches the acetabular component position in the intraoperative image.The method effectively transforms the templating exercise from one ofpreoperative estimation and planning to one of precision-guidedintraoperative analysis. The acetabular component placement isfacilitated by the scaling and alignment of the preoperative andintraoperative images described above.

In alternative constructions, a physical device, sensors, calipermeasurement of directly observable anatomical landmarks, or some otherform of mechanical and electrical hardware may be used to create imagescaling as a substitute for scaling based on the acetabular component.One example of an alternative construction (although not as precise)would be to measure the extracted femoral head using calipers, and thento scale the image by marking the femoral head in the preoperativeimage. In this method, absolute scaling is initially created in thepreoperative image, and then propagated to the intraoperative image byscaling and aligning consistent stationary bases.

The process continues with step 1909, FIG. 68B, by IntraoperativeTemplating Module 1862, with the system or user positioning a femoralstem template directly on top of the femoral stem in the intraoperativeimage. As with the acetabular component template process describedabove, this step is used to determine intraoperative data that will beused later in the method. FIG. 65 is a schematic screen view 1800similar to FIG. 64, demonstrating positioning of the femoral stemtemplate in the intraoperative image. The figure shows the acetabularcomponent outline 1774′ overlaid on the femoral head on the left-hand,preoperative image 1801. The user selects the femoral stem template usedin surgery, identified for this implant 1732 as “Depuy Corail AMT Size:Size 9, Offset: COXA VARA, Head: 5”, and the system renders the templatefor this model on the screen. The user or system overlays the templateimage 1804, within rectangle 1802, of the prosthesis 1732, directly ontop of the observed femoral component in the intra-operative image 1803.Initial calculations of Offset Changes and Leg Length Changes are notyet relevant, but are displayed in one corner of screen 1800 by indicia1812 including “Offset Changes: −272.0 mm”, and “Leg Length Changes:−12.7 mm”, along with “Abduction Angle: 45.0”. Control icon 1808 for theacetabular cup and an icon 1810 for the femoral stem template 1802 and1804 are provided in another portion of screen view 1800.

Note dashed 1820 extending from the neck of the implant 1732 over thegreater trochanter, and a parallel dashed line 1822 which touches theshoulder of implant 1732. (The user identified the shoulder of thefemoral prosthesis 1732, also referred to as the superolateral border ofthe femoral prosthesis, in the intraoperative image illustrated in FIG.62 above.) The system draws both lines 1820 and 1822 perpendicular tothe femoral axis and is guided by user positioning of markers thatidentify the greater trochanter and shoulder implant.

In step 1910, FIG. 68B, the system identifies the distance between theshoulder of the implant and the greater trochanter along the femoralaxis line, as shown in FIG. 65. In one construction, this process issupported by dashed reference lines 1820 and 1822 which are generated tobe perpendicular to femoral axis line 1752, identified earlier in theprocess and displayed in FIG. 66. The calculated distance between lines1820 and 1822, along the femoral stem axis, is intraoperative data thatwill be applied to the placement of the femoral stem template in thepreoperative image.

In step 1912, the system takes the calculated distance described aboveand generates a line in the preoperative image that is perpendicular tothe femoral axis line and is the same distance away from the greatertrochanter, as shown in FIG. 66. For step 1914, the system places thefemoral stem template in the preoperative image, using the linegenerated in step 1912.

FIG. 66 is a schematic screen view 1830 similar to FIG. 65 showing thefemoral stem template 1804′, within a rectangle 1802′, placed on thepre-operative image 1801′ superimposed and aligned with the femur F_(R).The system automatically repositions the femoral stem template 1804′ inpreoperative image 1801′ by using intraoperative data gathered from theplacement of the same template in the intraoperative image.Specifically, the system draws guidance lines and determines the implantposition on the femur in the preoperative image through the followingsteps:

-   -   The system draws dashed line 1832 through the greater trochanter        point (as previously identified by a marker) and perpendicular        to the femoral axis in the preoperative image (which may be        different than the intraoperative femoral axis).    -   The system takes the calculated distance, along the femoral        axis, between the greater trochanter and the shoulder of the        implant from the intraoperative image. The system generates        dashed line 1834 in the preoperative image below the greater        trochanter line 1832, and perpendicular to the femoral axis,        based on the distance calculated in the intraoperative image.    -   Line 1834 is generated as a visual guide for the user or system        to position the femoral stem template by placing the shoulder of        the femoral stem template on this line.    -   The system calculates the difference between the greater        trochanter and the shoulder of the prosthesis in the        intraoperative image along the femoral axis and perpendicular to        the femoral axis. The system then generates the location of the        femoral stem template in the preoperative image by replicating        the distance relative to the greater trochanter and placing the        shoulder of the prosthetic at that location.    -   Additionally, the femoral stem is automatically rotated so that        it maintains consistent angle relative to the femoral axis in        both images. For example, if the femoral axis is 15 degrees in        the intraoperative image and 10 degrees in the preoperative        image, the system will automatically rotate the femoral stem        template by 5 degrees when it moves it to the preoperative        image. Finally, the femoral stem template may be adjusted,        either by the user or automatically by the system, to match the        location of the femoral canal (i.e. movement of the femoral stem        template perpendicular to the femoral axis).    -   Having combined intraoperative data with preoperative imaging,        the system now precisely calculates, in step 1916 and        Differential Analysis Module 1864, the offset and leg length        differences based on the positioning of the femoral stem and        acetabular cup templates in the preoperative image.    -   Finally, the user can now modify, in step 1918, implant template        selections in the system to perform “what if analysis” and to        proactively analyze how intraoperative implant changes will        affect offset and leg length calculations, allowing        intraoperative changes and decision making to be based on        calculations made even before inserting a different implant        during surgery. The system or user will then place the new        implant selection using dashed line 1834 and other guidelines,        and will automatically calculate anticipated offset and leg        length changes by combining the template technique with the        intraoperative data being used.

The Offset and Leg Length change calculations are displayed in onecorner of screen 1830 by indicia 1812′ including “Abduction Angle:45.0”, “Offset Changes: 4.2 mm”, and “Leg Length Changes: −0.2 mm”. Alsoidentified is “Pinnacle Acetabular Cup Size: 54 mm” and “Depuy CorailAMT Size: Size 9, Offset: COXA VARA, Head: 5” for implant 1732 in thisexample. Control icon 1808′ for the acetabular cup and an icon 1810′ forthe femoral stem template 1802′ and 1804′ are provided in anotherportion of screen view 1830. In one construction, dashed reference lines1832 and 1834 are generated to be perpendicular to femoral axis line1706′.

In some constructions, the system will begin with the JointPointAnterior process and finish with the Reverse Templating system. Most ofthe data required to do Reverse Templating can be carried over fromJointPoint Anterior by the system so that very few steps are required bythe system to process the Reverse Templating technique.

FIG. 70 is an overlay image 2000 of a preoperative hip image 2001 and anintraoperative hip image 2003 having a trial implant 2002 in a hip withthe acetabular component 2004 transacted by stationary base lines 2006and 2007 extending between a first point 2008 on the obturator foramenOF and a second point 2010 on the anterior inferior iliac spine AIIS ofthe ileum. Also shown are two error analysis triangles 2020 (solidlines) and 2030 (dashed lines). Circles 2022 and 2032 in thisconstruction represent a landmark point on the greater trochanter inimages 2001 and 2003, respectively. Image 2000 is a representation ofpreoperative and intraoperative hip images 2001 and 2003 overlaidaccording to stationary base lines 2006 and 2007, respectively. Threeidentical pelvic points 2024, 2026, 2028 and 2034, 2036, 2038 in images2001 and 2003, respectively, have been identified, with the system 200,FIGS. 4C-4F, generating triangles 2020 and 2030 for each image asrepresented by FIG. 70. The triangles 2020 and 2030 can be visuallycompared to analyze the error in the anatomic area containing thestationary bases which, in this case, is the pelvis. A numericalconfidence score or other normalized numeric error analysis value mayalso be calculated and displayed in the system by calculating thedistance between points, comparing them to the length of the trianglevectors, and then normalizing the data, possibly using a log or othersuch nonlinear algorithm. The visual display and/or numerical confidencescore provides efficacy analysis in the construction. In other words,error analysis and correction is provided in some constructions for atleast one image, such as providing a confidence score or othernormalized numeric error analysis, and/or a visual representation of atleast one error value or error factor, such as relative alignment of oneor more geometric shapes, e.g. triangles, or symbols in two or moreimages.

In some constructions of the various alternative systems and techniquesaccording to the present invention, visual and/or audible userinstructions are sequentially generated by the system to guide the usersuch as “Draw line along Pubic Symphysis”. Guidance for surgeryutilizing other types of implants, and for other surgical procedures,including partial or total knee or shoulder replacements and footsurgery as well as wrist surgery, will occur to those skilled in the artafter reading this disclosure. Also, other types of medical imagingusing energy other than visible light, such as ultrasound, may beutilized according to the present invention instead of actual X-rays.Moreover, if a computer interface tool, such as a stylus or light pen,is provided to the user in a sterile condition, than the user can remainwithin a sterile field of surgery while operating a computing deviceprogrammed according to the present invention.

Although specific features of the present invention are shown in somedrawings and not in others, this is for convenience only, as eachfeature may be combined with any or all of the other features inaccordance with the invention. While there have been shown, described,and pointed out fundamental novel features of the invention as appliedto one or more preferred embodiments thereof, it will be understood thatvarious omissions, substitutions, and changes in the form and details ofthe devices illustrated, and in their operation, may be made by thoseskilled in the art without departing from the spirit and scope of theinvention. For example, it is expressly intended that all combinationsof those elements and/or steps that perform substantially the samefunction, in substantially the same way, to achieve the same results bewithin the scope of the invention. Substitutions of elements from onedescribed embodiment to another are also fully intended andcontemplated.

It is also to be understood that the drawings are not necessarily drawnto scale, but that they are merely conceptual in nature. Otherembodiments will occur to those skilled in the art and are within thescope of the present disclosure.

What is claimed is:
 1. A system to analyze images at a surgical sitewithin a patient, comprising: an image selection module to acquire (i)at least a first, reference image including one of a preoperative imageof the surgical site and a contralateral image on an opposite side ofthe patient from the surgical site, and (ii) at least a second, resultsimage of the site; a data input module that receives the first andsecond images and generates at least two points to establish a firststationary base and a second stationary base on at least one anatomicalfeature that is present in each of the first and second images,respectively; and an analysis module that utilizes the stationary basein each image to provide at least one of (a) overlaying the first andsecond images and comparing at least one of bone alignment, scaling andimplant alignment within the images and (b) analyzing at least one ofimage rotation, image alignment, scaling, offset, abduction angle,length differential and orientation of at least one of a bone and animplant within the images.
 2. The system of claim 1 wherein the firstand second images are provided by the image selection module to the datainput module in a digitized format.
 3. The system of claim 1 wherein atleast one dimension of each of the first and second stationary bases isretrievably stored in at least one storage medium as a count of pixelsfor that dimension, and the analysis module utilizes the pixel count forthat dimension.
 4. The system of claim 1 wherein the analysis moduleutilizes the stationary base in a selected one of the first and secondimages to provide at least relative scaling of the other of the firstand second images to the match the scaling of the selected one of thefirst and second images.
 5. The system of claim 1 wherein the analysismodule utilizes at least one object of known dimension in at least oneof the first and second images to provide absolute scaling to at leastthat image.
 6. The system of claim 1 wherein the analysis module rotatesat least one of the first and second images relative to the other of thefirst and second images so that both images are aligned according totheir respective stationary bases.
 7. The system of claim 1 wherein thedata input module generates at least one landmark point for each imagethat is spaced from the stationary base in that image.
 8. The system ofclaim 7 wherein the analysis module utilizes the landmark points toassist alignment of the first and second images relative to each other.9. The system of claim 7 wherein the analysis module utilizes thelandmark points to position a digital template on at least one of thefirst and second images.
 10. The system of claim 1 further including atemplate input module that provides at least one digital template thatis superimposed over at least one feature in at least one of the firstand second images.
 11. The system of claim 10 wherein the at least onedigital template is matched to at least one feature in each of the firstand second images.
 12. The system of claim 10 wherein the at least onedigital template is matched to an implant in the second, results imageand then the digital template is superimposed on the first, referenceimage to analyze at least one parameter of at least one bone of thepatient.
 13. The system of claim 1 further include a display to provideat least visual guidance to a user of the system.
 14. The system ofclaim 1 wherein the first image is a contralateral image that is flippedand overlaid on the second image.
 15. The system of claim 1 wherein thefirst image is a contralateral image, the data input module generates acommon stitching line in each image, and the first and second images arestitched together to form a unitary view of both sides of the patient.16. A system to analyze images at a surgical site within a patient,comprising: an image selection module to acquire (i) at least a first,reference image in a digitized format including one of a preoperativeimage of the surgical site and a contralateral image on an opposite sideof the patient from the surgical site, and (ii) at least a second,results image of the site in the digitized format; a data input modulethat receives the first and second images and generates at least twopoints to establish a first stationary base and a second stationary baseon at least one anatomical feature that is present in each of the firstand second images, respectively, and generates at least one landmarkpoint for each image that is spaced from the stationary base in thatimage; a display to provide at least visual guidance to a user of thesystem including showing at least the position of the first and secondstationary bases on the first and second images, respectively; whereinat least one dimension of each of the first and second stationary basesis retrievably stored in at least one storage medium as a count ofpixels for that dimension; and an analysis module that utilizes at leastthe pixel count for the stationary base in each image to provide atleast one of (a) overlaying the first and second images and comparing atleast one of bone alignment, scaling and implant alignment within theimages and (b) analyzing at least one of image rotation, imagealignment, scaling, offset, abduction angle, length differential andorientation of at least one of a bone and an implant within the images.17. A method for analyzing images to optimize the restoration oforthopaedic functionality at a surgical site within a patient,comprising: acquiring (i) at least a first, reference image includingone of a preoperative image of the surgical site and a contralateralimage on an opposite side of the patient from the surgical site, and(ii) at least a second, results image of the site; generating at leasttwo points to establish a first stationary base and a second stationarybase on at least one anatomical feature that is present in each of thefirst and second images, respectively; and utilizing the stationary basein each image to provide at least one of (a) overlaying the first andsecond images and comparing at least one of bone alignment, scaling andimplant alignment within the images and (b) analyzing at least one ofimage rotation, image alignment, scaling, offset, abduction angle,length differential and orientation of at least one of a bone and animplant within the images.
 18. A method for optimizing sizing andplacement of an implant at a surgical site within a patient, comprising:obtaining at least a first, pre-operative digital image of the surgicalsite along a first viewing angle, the first image including at least afirst anatomical feature; obtaining a direct measurement of one of (a) aportion of the first anatomical feature and (b) an initial implantpositioned at the surgical site; scaling the first image based on thedirect measurement to generate an accurately scaled first image;selecting an initial implant and placing the initial implant at thesite; obtaining at least a second, intra-operative digital image of thesite with the initial implant along the first viewing angle; andanalyzing the placement of the initial implant including comparing thesecond image with the accurately scaled first image.
 19. The method ofclaim 18 wherein analyzing includes estimating an optimally-configuredimplant.
 20. The method of claim 19 further including selecting a finalimplant based on the optimally-configured implant.
 21. The method ofclaim 18 further including generating an estimated measurement of thefirst anatomical feature utilizing the first image, and wherein scalingthe first image includes calculating a difference between the estimatedmeasurement and the direct measurement.
 22. The method of claim 18wherein at least analyzing the placement includes comparing the secondimage with the accurately scaled first image on a mobile computingdevice.
 23. The method of claim 18 wherein analyzing includes comparingthe first anatomical feature with a corresponding contra-lateralanatomical feature of the patient.
 24. The method of claim 18 whereinthe site includes a joint of the patient.
 25. The method of claim 24wherein the first anatomical feature is located on a portion of a bonypart of the patient to be replaced.
 26. The method of claim 25 whereinobtaining the direct measurement includes excising the bony part fromthe patient, and measuring at least one dimension of the firstanatomical feature in a direction transverse to the first viewing angle.